Am J Hum Genet 27:755-764, 1975
Kniest Syndrome with Dominant Inheritance and Mucopolysacchariduria HYON J. KIM,' N. G. BERATIS,1 PAULA BRILL,2 E. RAAB,3 K. HIRSCHHORN,' AND R. MATALON4
The Kniest syndrome, previously considered a variant of metatropic dwarfism, was originally described in 1952 [1]. It has been called metatropic dwarfism type II or pseudometatropic dwarfism [2]. In fact, two cases of the Kniest syndrome have been reported as metatropic dwarfism [3, 4]. Recently, however, Rimoin et al. [5] and Siggers et al. [6] recognized the Kniest syndrome as a distinct entity. Most reported cases have been sporadic, and urinary mucopolysaccharide studies, if performed, have revealed normal total excretion. The syndrome is manifested by the following: short-trunk dwarfism, kyphoscoliosis, enlargement of joints with limited motion, bell-shaped chest, flat facies, prominent eyes, myopia, deafness, cleft palate, retarded motor milestones, tibial bowing, and recurrent respiratory and middle ear infections. Early in life, patients present with short, deformed extremities and a relatively long trunk. Later in childhood kyphoscoliosis and lordosis develop causing the disproportionate shortening of the trunk. This study describes a mother and daughter with clinical and radiologic findings typical of the Kniest syndrome. The case demonstrates dominant inheritance and abnormal mucopolysaccharide excretion. CASE REPORTS
The proband (ML280461), a female, was the product of a full-term pregnancy delivered by Caesarean section. Both parents, aged 29, were from Puerto Rico, but no consanguinity was discovered. The prenatal history and the perinatal course were uneventful. Detailed developmental milestones were not accurately remembered by the mother. At 18 months the child was examined at the orthopedic clinic because of a waddling Received January 14, 1975; revised April 4, 1975. This work was supported by U.S. Public Health Service grant HD 02552 and Genetics Center grant GM 19443. K. Hirschhorn is a career scientist of the Health Research Council of the City of New York (I-513). 1 Division of Medical Genetics, Department of Pediatrics, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 2 Department of Radiology, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 3 Department of Ophthalmology, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 4 Department of Pediatrics, University of Chicago, Chicago, Illinois 60637. i 1975 by the American Society of Human Genetics. All rights reserved.
755
756
KIM ET AL.
gait, and the diagnosis of Morquio syndrome was considered. She had frequent otitis media and respiratory infections. When we examined her at the age of 13 years, her height was 129 cm and weight 22 kg, both below the third percentile. The span was 132 cm, while the upper and lower segments were 61 and 68 cm, respectively. The facies was flat with prominent eyes, mild synophrys, epicanthal folds, midfacial hypoplasia, flat nasal bridge, short upturned nose, and increased distance between nose and philtrum (fig. 1).
FIG. 1.-Facial features of proband
The teeth were hypoplastic and abnormally aligned. There was dorsal thoracic kyphosis and flaring of lower rib cage. The knees, ankles, wrists, elbows, and interphalangeal joints were enlarged (fig. 2). The motion of the joints was limited. A grade II/VI soft systolic murmur was heard only at the apex. There was moderately severe mixed sensory-neural and conductive deafness in the right ear and sensory-neural deafness in the left. Severe myopia was present, the corneas were clear, and the fundi showed evidence of early mild chorioretinal atrophy. Electroretinography showed responses in both eyes at the low borderline of the normal range. These findings are consistent with a possible mild retinal dysfunction, possibly due to the ophthalmoscopically visible retinal thinning and early atrophy which frequently accompanies severe myopia [7; 8, p 241]. The patient appeared to have normal intelligence. The patient's 43-year-old mother (ML100930) had a height of 131 cm and a span of 157 cm. Her appearance (fig. 3) was strikingly similar to that of her daughter. Her hearing ability was severely affected bilaterally. The right eye became blind and atrophic after an operation for cataract was performed at the age of 25 years. The left eye was severely myopic and contained a nuclear cataract. The refractive error of the left eye was in the same range present in the daughter, well beyond the usual degree of secondary myopia which can accompany a nuclear cataract. The cornea was entirely clear. She demonstrated the expected extinguished electroretinographic response in her degenerated right eye. Responses from the left eye were slightly subnormal in amplitude, with increased implicit times and loss of oscillatory potentials. These findings were felt to be consistent with mild retinal dysfunction despite the myopia known to be present. The father of the proband was phenotypically normal, as were her two male siblings. Blood group typing and HL-A histocompatibility antigens confirmed that he was the patient's father. The maternal grandparents were reported as normal. On both mother and daughter, complete blood counts, urine analysis, and serum calcium and phosphorus levels were normal. Amino acid screening was negative in both urine and serum. No inclusion bodies were found in leukocytes of peripheral blood smears.
KNIEST SYNDROME
FIG. 2.-Proband at 13 years of age
FIG. 3.-Mother at 43 years of age
757
758
KIM ET AL.
The radiographic configuration of the skeleton was strikingly similar in both daughter and mother. Consistent with the daughter's age, epiphyseal fusion had not yet occurred. Consequently, abnormal bone formation could be recognized on both the epiphyseal and metaphyseal sides of the growth plate. In the mother, marked degenerative changes were superimposed on several of her abnormal joints. The main radiographic findings were: irregularity and flattening of vertebral bodies, severe thoracic kyphosis (fig. 4a), and bulbous ends of the long bones with epiphyseal and metaphyseal abnormalities including irregular ossification on both sides of the epiphyseal plate (fig. 4b). Abnormalities were also noted in the pelvis, thorax, skull, hands, and feet. Pelvic radiographs showed numerous abnormalities. Both patients had short, wide femoral necks with varus deformities. The femoral capital epiphyses of the daughter were markedly flattened (fig. 4c). There was striking expansion of the proximal femur of the mother with obliteration of the usual transition between femoral head and neck. The iliac, pubic, and ischiac bones were all hypoplastic. The interpedicular distances of the lumbar spine narrowed caudally. In the mother complete bony fusion of the symphysis pubis was seen. The upper rib cage had a narrow transverse diameter while the lower ribs flared laterally. The bones in the proximal carpal row were small and irregular in the mother, and all the joint spaces of her hand were narrowed. Both patients showed squaring of the metacarpophalangeal joints. In the feet the second through fifth metatarsals were abnormally thin and the fourth metatarsals were short as well. A small sella turcica and prominence of the odontoid process of the second cervical vertebra were seen in lateral radiographs of the skull and upper cervical spine (fig. 4d). In the proband, increased distance between the odontoid and the anterior arch of the first cervical vertebra was also present. SPECIAL STUDIES
Acid mucopolysaccharides (AMPS) in urine were isolated according to the method described by Dorfman and Matalon [9] using gel chromatography with Sephadex G-25. This was followed by precipitation of the AMPS fraction with dropwise addition of cetylpyridinium chloride. Care was taken not to add excessive amounts of cetylpyridinium chloride, since keratan sulfate and some heparan sulfate may be redissolved. Therefore, the supernatant fluid was reprecipitated with 6 vol of ethanol, electrophoresed, and -analyzed for the presence of AMPS. The AMPS-cetylpyridinium complex was dissolved in 2 M lithium chloride and the AMPS reprecipitated with 4 vol of ethanol. The precipitate was dried with ethanol and ether and then dissolved with water and used for electrophoresis and further studies. The analytical methods included the determination of uronic acid by the carbazole method of Dische [10]. Hexosamine was determined by the Boas modification of the Elson-Morgan method [11]. Total sulfate content was estimated by Muir's modification of the Dodgson and Spencer technique [12]. Carbohydrates were determined by the phenol method [13], and N-sulfated hexosamine was determined by the nitrous acid reaction as described by Lagunoff and Warren [14]. Electrophoresis of AMPS was performed on cellulose polyacetate strips (sepraphore III) as described by Matalon and Dorfman [15]. The latter technique permits quick screening for both the presence of AMPS and their electrophoretic mobility. Using these methods AMPS were isolated from two urine samples of the proband and two from her mother. From 24-hr urine samples of the proband, 30.8 mg and 19.8 mg AMPS were isolated. These amounts are excessive, since normal controls
KNIEST SYNDROME
759
a
b
d
FIG. 4.-Radiographs of proband (a-c) and mother (d). a, Lateral radiograph of mid- and
lower-thoracic spine. Note severe kyphosis with apex at T6 which is wedged anteriorly (arrow); vertebral bodies are flattened, irregular, and increased in anteroposterior diameters. b, Frontal radiograph of right ankle. Note irregular ossification on both sides of tibial and fibular epiphyseal plates and amorphously increased density in metaphyseal regions and osteoporosis of epiphyses and diaphyses. c, Radiograph of left hip. Femoral capital epiphysis is extremely flattened. Note coxa vara with shortening and thickening of femoral neck; acetabulum is irregular and hip joint space narrowed. d, Lateral radiograph of skull and upper cervical spine of mother. Sella turcica is small; odontoid process of second cervical vertebra (black arrow) is increased in anteroposterior diameter; decrease in height of body of third cervical vertebra (white arrow).
760
KIM ET AL.
of the same age yield less than 10 mg/24 hr. Considering the weight of the proband (22 kg), normal urines should seldom exceed 5 mg/24 hr. From two 24-hr urine samples of the mother, 18.6 mg and 15.2 mg AMPS were isolated. These amounts are also excessive, since normal controls for the same age have not exceeded 4-5 mg/24 hr. Electrophoresis of the AMPS excreted by the proband and her mother revealed mobility similar to standard keratan sulfate (gift of Dr. J. A. Cifonelli). The ratios of uronic acid to hexosamine were less than one in all samples: in the proband's urine they were 0.75 and 0.65, and in the mother, 0.40 and 0.48. These ratios are compatible with keratan sulfate but also with dermatan sulfate. Thus purification of the material isolated and further identification had to be carried out. In order to detect the presence of dermatan sulfate, which may give a low carbazole:hexosamine ratio, the material was treated with CuSO4 for precipitation of dermatan sulfate [16]. Only about 1.5%o of the material precipitated, while the bulk remained in the supernatant. The supernatant can include chondroitin 4/6sulfate, keratan sulfate, and heparan sulfate. We were unable to detect N-sulfated hexosamine, which is specific for heparin sulfate (and heparin), thus ruling out the presence of heparan sulfate. When the AMPS were subjected to chondroitinase ABC and then chromatographed on Sephadex G-25 [17], 94%o of the material was eluted in the void volume indicating nonsusceptibility to chondroitinase ABC, while only 6%o was included in the dissaccharide region. The elution pattern from Dowex 1, X 2 Clwas further examined and found to be characteristic of keratan sulfate since the major fraction was eluted with 4.0 M NaCl. The sulfate content of this fraction was determined; the SO4:hexosamine ratio was 1.02 for the proband and 1.03 for the mother. The uronic:hexosamine ratio in this fraction was 0.25, further indicating a pattern typical of keratan sulfate. These data indicate that both the proband and her mother excrete excessive amounts of polysaccharide and that this material was indeed keratan sulfate. Cultured skin fibroblasts of both mother and proband were highly metachromatic. The lysosomal enzymes, arylsulfatase A and B, a-N-acetylhexosaminidase, a glucosidase, a galactosidase, a iduronidase, a mannosidase, a fucosidase, /8-Nacetylhexosaminidase, /8 galactosidase, P glucosidase, and /8 glucuronidase studied in cultured skin fibroblasts from the mother and daughter by standard methods [18, 19] or modifications [20] were normal. Deficiency of the lysosomal enzyme chondroitin sulfate N-acetylhexosamine sulfate sulfatase has been demonstrated in Morquio syndrome [21]. This enzyme also had normal activity in the mother's fibroblasts. DISCUSSION
The Kniest syndrome should be differentially diagnosed from other forms of short-trunk dwarfism, especially spondyloepiphyseal dysplasia congenita (SED), Morquio syndrome, and metatropic dwarfism. These four chondrodystrophies primarily involve the spine causing platyspondyly which leads to short-trunk dwarfism.
KNIEST SYNDROME
761
In all there is a varying degree of epiphyseal and metaphyseal involvement of the tubular bones. The skeletal manifestations are present at birth in SED, metatropic dwarfism, and probably in the Kniest syndrome. However, Morquio syndrome is only recognizable later in life. Both metatropic dwarfism and Kniest syndrome present with short limbs and a relatively long trunk in early infancy, while in late infancy kyphoscoliosis develops resulting in short-trunk dwarfism. In SED shorttrunk dwarfism is present at birth. The combination of radiographic findings seen in our cases is similar to that previously described in the Kniest syndrome [1-6]. Platyspondyly and vertebral irregularity, metaphyseal flaring, and irregular ossification on both sides of the epiphyseal plate have been recognized as outstanding features of this syndrome [5, 6]. Each of the present cases had an unusually small sella turcica, as did Kniest's original patient. In many respects the Kniest syndrome resembles SED. In SED [21], the most severe vertebral hypoplasia tends to be at the thoraco-lumbar junction, while in our patients the wedged vertebrae at the apex of the kyphosis were in the midthoracic spine. The shape of the thorax is broad in SED rather than narrowed superiorly as in our patients. The configuration of the pelvis and femoral head and neck is similar except for flattening of the acetabular roof in SED. Although the ends of the bones are not as bulbous in SED, dome-shaped metaphyses with central bulging into the epiphyses, as seen in our proband, have been described in SED. Abnormalities of carpal ossifications, especially affecting the proximal row as seen in the mother, may be present in both conditions. The large odontoid in our patients is of considerable interest as a possible differentiating feature. In a review of the literature, Spranger and Langer [22] found odontoid hypoplasia in all patients with SED who were over 1 year of age. Morquio syndrome, while exhibiting obvious abnormalities of the spine, pelvis, and long bones, differs somewhat from the present cases. The pelvis in Morquio syndrome shows supraacetabular constriction, coxa valga, and narrow femoral necks. The apex of the kyphosis tends to be near the thoraco-lumbar junction, and beaked vertebral bodies are seen. The hands of the present cases show no tendency to the proximal metacarpal pointing of Morquio syndrome. Again, as in SED, the odontoid is hypoplastic. In Morquio syndrome, the lumbar bodies tend to be more severely affected than the thoracic. The reverse was true in the present cases. Numerous other bone changes of Morquio disease were lacking [2]. The Kniest syndrome is radiographically quite similar to metatropic dwarfism. Both show vertebral abnormalities, but platyspondyly is more marked in metatropic dwarfism. In both conditions there may be caudal narrowing of interpedicular distances. The fibula is frequently long in metatropic dwarfism and was of normal length in our patients. While both types of dwarfism show dumbell-shaped long bones, the irregular ossification on both sides of the epiphyseal plate is characteristic of the Kniest syndrome, as is the squaring of the metacarpophalangeal joints and narrowing of the joint spaces of the hands. In our patients the iliac bones were small and without the characteristic crescent shape described in metatropic dwarf-
762
KIM ET AL,
ism. Neither the small sella turcica nor prominent odontoid are typical of metatropic dwarfism. Extraskeletal manifestations present in these disorders are helpful for the diagnosis of these entities. The Kniest and Morquio syndromes and SED all have characteristic facies, but the face appears normal in metatropic dwarfism. Myopia and retinal detachment are frequently observed in SED. Corneal clouding develops in Morquio syndrome, and myopia has been reported in the Kniest syndrome. The electroretinographic abnormalities in the mother and daughter are inconclusive for the retinal degenerative disease which can occur in several of the mucopolysaccharidoses [23]. Serial determinations will be required to detect an abnormal response beyond what can occur in myopic eyes. It should also be noted that the history of cataract in the mother at age 25, and even the presence of a well developed cataract at age 43 years, anticipates by several decades the usual appearance of acquired lens opacities not due to trauma or preexisting intraocular inflammation. The daughter does not show abnormalities of the crystalline lenses at this time. It is possible that these will appear later, but still at a relatively early age; if so, they may constitute another component of this syndrome. Frequent otitis media and hearing loss has been observed in both Morquio and Kniest syndromes. The deafness in both may be of conductive or sensory-neural origin. Urinary excretion of keratan sulfate is present in Morquio syndrome, but no excess of mucopolysaccharide has been found in SED or metatropic dwarfism. The finding of increased amounts of AMPS in the urine of both of our patients has not been previously reported in the Kniest syndrome. In addition, there is a specifically high level of keratan sulfate comprising over 90%o of the polysaccharides isolated. Considering that normal urine contains only trace amounts of keratan sulfate [24], it must be assumed that the finding of keratan sulfaturia in the two patients described is directly related to the genetic defect. However, the isolation of keratan sulfate from urine and its documentation should always be approached with caution. Therefore, a step by step approach to exclude other mucopolysaccharides or glycoproteins was undertaken. Amounts of keratan sulfate in urine should be correlated with age, since Linder et al. [25] have shown in 12 patients that keratan sulfate excretion declines with age. This may account for the lower levels of keratan sulfate in the mother's urine. Despite the keratan sulfaturia, our two patients were enzymatically different from Morquio syndrome. A deficiency of N-acetylhexosamine 6-sulfate sulfatase has been found in Morquio disease [21]. When fibroblasts from one of our patients were assayed for N-acetylhexosamine 6-sulfate sulfatase, they were found to possess normal levels. While some of the previously reported patients with the Kniest syndrome have not demonstrated elevated amounts of total AMPS in the urine, not all such patients have been tested. Our report makes it apparent that the Kniest syndrome may be heterogeneous, with some patients excreting large quantities of keratan sulfate. This group may represent a new mucopolysaccharidosis with dominant inheritance.
KNIEST SYNDROME
763
The mode of inheritance has been established in SED as autosomal dominant and in both Morquio syndrome and metatropic dwarfism as autosomal recessive. The cases of Kniest syndrome reported in the literature have generally been sporadic except for two patients, a mother and a daughter, studied by Maroteaux and Spranger [26]. These cases, together with ours, suggest a dominant mode of inheritance in at least some cases of Kniest syndrome. Since no male-to-male transmission has yet been reported, it is not known whether the mutant gene which causes the Kniest syndrome is on an autosome or the X chromosome. The mean paternal age in the eight cases reported so far was calculated as 28½/2 years [6]. In view of the pattern of dominant inheritance observed in our family and the recessive inheritance in Morquio syndrome (both with urinary keratan sulfate excretion), it may be hypothesized that while Morquio syndrome is caused by the deficiency of an enzyme responsible for the degradation of keratan sulfate [21], the cases of the Kniest syndrome reported here may be due to an inhibitor of this enzyme or a mutation in another regulatory gene affecting this pathway. SUMMARY
A mother and daughter with clinical and radiographic findings typical of the Kniest syndrome are reported. It is apparent that this syndrome is dominantly inherited and that sporadic cases may represent fresh mutations. Abnormally high keratan sulfate excretion was found, indicating that the Kniest syndrome is a mucopolysacchariduria. ACKNOWLEDGMENTS We thank Drs. J. Dorst and D. Rimoin for helpful discussions. 1. 2. 3. 4. 5. 6.
7. 8.
9.
REFERENCES KNIEST W: Zur Abgrenzung der dysostosis euchondralis von der chondrodystrophie. Z. Kinderheilkd 70:633-640, 1952 McKusIcK VA: Mucopolysaccharidosis IV, in Heritable Disorders of Connective Tissue, 4th ed, edited by McKusIcK VA, St. Louis, Mosby, 1972, pp 583-611 LAROSE JH, GAY BB: Metatropic dwarfism. Am J Roentgenol Radium Ther Nucl Med 106:156-161, 1969 SILVERMAN FN: Introduction: skeletal dysplasias. Birth Defects: Orig Art Ser 10(9) :ix-xiv, 1974 RIMOIN DL, HOLLISTER DW, SIGGERS P, SILBERBERG R, LACHMAN R, McALISTER W, KAUFMAN R, McKUsICK VA, DORST J: Clinical, radiographic, histologic and ultra structural definition of the Kniest syndrome (abstr.). Pediatr Res 7:348, 1973 SIGGERs D, RIMOIN D, DORST P, DOTY S, WILLIAMS B, HOLLISTER D, SILBERG R, CRANLEY R, KAUFMAN R, McKuSICK VA: The Kniest syndrome. Birth Defects: Orig Art Ser 10(9) :193-208, 1974 JACOBSON JH: Clinical Electroretinography. Springfield, Ill., Thomas, 1961, pp. 148151 KRILL AE: Hereditary Retinal and Choroidal Diseases, vol. 1. Hagerstown, Md., Harper & Row, 1972 DORFMAN A, MATALON R: The mucopolysaccharidoses, in The Metabolic Basis of Inherited Disease, 3d ed, edited by STANBURY JB, WYNGAARDEN JB, FREDRICKSON DS, New York, McGraw-Hill, 1972, pp 1218-1272
764
KIM ET AL.
10. DISCHE Z: A new specific color reaction for glucuronic acid. J Biol Chem 171:725730, 1947 11. BOAS NG: Method for the determination of hexosamines in tissues. J Biol Chem 204:553-563, 1953 12. MUIR H: The nature of the link between protein and carbohydrate of a chondroitin sulfate complex from hyaline cartilage. Biochem J 69:195-204, 1958 13. DUBOIS M, GILLES KA, HAMILTON JK, REBERS PA, SMITH F: Colorimetric method for determination of sugars and related substances. Anal Chem 28:350-356, 1956 14. LAGUNOFF D, WARREN G: Determination of 2-deoxy-2-sulfaminohexose content of mucopolysaccharides. Arch Biochem Biophys 99:396-400, 1962 15. MATALON R, DORFMAN A: Hurler's syndrome: biosynthesis of acid mucopolysaccharides in tissue culture. Proc Natl Acad Sci USA 56:1310-1316, 1966 16. CIFONELLI JA, LuDoWIEG J, DORFMAN A: Chemistry of 18-heparin (chondroitin sulfate B). J Biol Chem 233:541-545, 1958 17. ROBINSON HC, DORFMAN A: The sulfation of chondroitin sulfate in embryonic chick cartilage epiphyses. J Biol Chem 244:348-352, 1969 18. MATALON R, DORFMAN A: Hurler's syndrome: an a-L-iduronidase deficiency. Biochem Biophys Res Commun 47:959-964, 1972 19. WEISSMANN B, RoWIN G, MARSHALL J, FREIDERICI D: Mammalian a-acetylglucosaminidase: enzymic properties, tissue distribution and intercellular localization. Biochemistry 6:207-214, 1967 20. BERATIS NG, TURNER BM, WEISS R, HIRSCHHORN K: Arylsulfatase B deficiency in Maroteaux-Lamy syndrome. Pediatr Res 9:475-480, 1975 21. MATALON R, ARBOGAST B, DORFMAN A: Morquio's syndrome: a deficiency of chondroitin sulfatase N-acetylhexosamine sulfate sulfatase. Biochem Biophys Res Commun 61:759-765, 1974 22. SPRANGER JW, LANGER LO: Sponylo-epiphyseal dysplasia congenita. Radiology 94: 313-322, 1970 23. GILLS JP, HOBSON R, HANLEY WB, MCKUSICK VA: Electroretinography and fundus oculi findings on Hurler's diseases and allied mucopolysaccharidosis. Arch Ophthalmol 74:596-603, 1965 24. VARADI DP, CIFONELLI JA, DORFMAN A: The acid mucopolysaccharides in normal urine. Biochim Biophys Acta 141:103-117, 1967 25. LINKER A, EVANS LR, MADSEN JA: Problems in the analysis of urinary mucopolysaccharide excretion. Biochem Med 2 :448-456, 1969 26. MAROTEAUX P, SPRANGER J : La maladie de Kniest. Arch Fr Pediatr 30:735-750, 1973
Kniest Syndrome with Dominant Inheritance and Mucopolysacchariduria HYON J. KIM,' N. G. BERATIS,1 PAULA BRILL,2 E. RAAB,3 K. HIRSCHHORN,' AND R. MATALON4
The Kniest syndrome, previously considered a variant of metatropic dwarfism, was originally described in 1952 [1]. It has been called metatropic dwarfism type II or pseudometatropic dwarfism [2]. In fact, two cases of the Kniest syndrome have been reported as metatropic dwarfism [3, 4]. Recently, however, Rimoin et al. [5] and Siggers et al. [6] recognized the Kniest syndrome as a distinct entity. Most reported cases have been sporadic, and urinary mucopolysaccharide studies, if performed, have revealed normal total excretion. The syndrome is manifested by the following: short-trunk dwarfism, kyphoscoliosis, enlargement of joints with limited motion, bell-shaped chest, flat facies, prominent eyes, myopia, deafness, cleft palate, retarded motor milestones, tibial bowing, and recurrent respiratory and middle ear infections. Early in life, patients present with short, deformed extremities and a relatively long trunk. Later in childhood kyphoscoliosis and lordosis develop causing the disproportionate shortening of the trunk. This study describes a mother and daughter with clinical and radiologic findings typical of the Kniest syndrome. The case demonstrates dominant inheritance and abnormal mucopolysaccharide excretion. CASE REPORTS
The proband (ML280461), a female, was the product of a full-term pregnancy delivered by Caesarean section. Both parents, aged 29, were from Puerto Rico, but no consanguinity was discovered. The prenatal history and the perinatal course were uneventful. Detailed developmental milestones were not accurately remembered by the mother. At 18 months the child was examined at the orthopedic clinic because of a waddling Received January 14, 1975; revised April 4, 1975. This work was supported by U.S. Public Health Service grant HD 02552 and Genetics Center grant GM 19443. K. Hirschhorn is a career scientist of the Health Research Council of the City of New York (I-513). 1 Division of Medical Genetics, Department of Pediatrics, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 2 Department of Radiology, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 3 Department of Ophthalmology, Mount Sinai School of Medicine of the City University of New York, 5th Avenue and 100th Street, New York, New York 10029. 4 Department of Pediatrics, University of Chicago, Chicago, Illinois 60637. i 1975 by the American Society of Human Genetics. All rights reserved.
755
756
KIM ET AL.
gait, and the diagnosis of Morquio syndrome was considered. She had frequent otitis media and respiratory infections. When we examined her at the age of 13 years, her height was 129 cm and weight 22 kg, both below the third percentile. The span was 132 cm, while the upper and lower segments were 61 and 68 cm, respectively. The facies was flat with prominent eyes, mild synophrys, epicanthal folds, midfacial hypoplasia, flat nasal bridge, short upturned nose, and increased distance between nose and philtrum (fig. 1).
FIG. 1.-Facial features of proband
The teeth were hypoplastic and abnormally aligned. There was dorsal thoracic kyphosis and flaring of lower rib cage. The knees, ankles, wrists, elbows, and interphalangeal joints were enlarged (fig. 2). The motion of the joints was limited. A grade II/VI soft systolic murmur was heard only at the apex. There was moderately severe mixed sensory-neural and conductive deafness in the right ear and sensory-neural deafness in the left. Severe myopia was present, the corneas were clear, and the fundi showed evidence of early mild chorioretinal atrophy. Electroretinography showed responses in both eyes at the low borderline of the normal range. These findings are consistent with a possible mild retinal dysfunction, possibly due to the ophthalmoscopically visible retinal thinning and early atrophy which frequently accompanies severe myopia [7; 8, p 241]. The patient appeared to have normal intelligence. The patient's 43-year-old mother (ML100930) had a height of 131 cm and a span of 157 cm. Her appearance (fig. 3) was strikingly similar to that of her daughter. Her hearing ability was severely affected bilaterally. The right eye became blind and atrophic after an operation for cataract was performed at the age of 25 years. The left eye was severely myopic and contained a nuclear cataract. The refractive error of the left eye was in the same range present in the daughter, well beyond the usual degree of secondary myopia which can accompany a nuclear cataract. The cornea was entirely clear. She demonstrated the expected extinguished electroretinographic response in her degenerated right eye. Responses from the left eye were slightly subnormal in amplitude, with increased implicit times and loss of oscillatory potentials. These findings were felt to be consistent with mild retinal dysfunction despite the myopia known to be present. The father of the proband was phenotypically normal, as were her two male siblings. Blood group typing and HL-A histocompatibility antigens confirmed that he was the patient's father. The maternal grandparents were reported as normal. On both mother and daughter, complete blood counts, urine analysis, and serum calcium and phosphorus levels were normal. Amino acid screening was negative in both urine and serum. No inclusion bodies were found in leukocytes of peripheral blood smears.
KNIEST SYNDROME
FIG. 2.-Proband at 13 years of age
FIG. 3.-Mother at 43 years of age
757
758
KIM ET AL.
The radiographic configuration of the skeleton was strikingly similar in both daughter and mother. Consistent with the daughter's age, epiphyseal fusion had not yet occurred. Consequently, abnormal bone formation could be recognized on both the epiphyseal and metaphyseal sides of the growth plate. In the mother, marked degenerative changes were superimposed on several of her abnormal joints. The main radiographic findings were: irregularity and flattening of vertebral bodies, severe thoracic kyphosis (fig. 4a), and bulbous ends of the long bones with epiphyseal and metaphyseal abnormalities including irregular ossification on both sides of the epiphyseal plate (fig. 4b). Abnormalities were also noted in the pelvis, thorax, skull, hands, and feet. Pelvic radiographs showed numerous abnormalities. Both patients had short, wide femoral necks with varus deformities. The femoral capital epiphyses of the daughter were markedly flattened (fig. 4c). There was striking expansion of the proximal femur of the mother with obliteration of the usual transition between femoral head and neck. The iliac, pubic, and ischiac bones were all hypoplastic. The interpedicular distances of the lumbar spine narrowed caudally. In the mother complete bony fusion of the symphysis pubis was seen. The upper rib cage had a narrow transverse diameter while the lower ribs flared laterally. The bones in the proximal carpal row were small and irregular in the mother, and all the joint spaces of her hand were narrowed. Both patients showed squaring of the metacarpophalangeal joints. In the feet the second through fifth metatarsals were abnormally thin and the fourth metatarsals were short as well. A small sella turcica and prominence of the odontoid process of the second cervical vertebra were seen in lateral radiographs of the skull and upper cervical spine (fig. 4d). In the proband, increased distance between the odontoid and the anterior arch of the first cervical vertebra was also present. SPECIAL STUDIES
Acid mucopolysaccharides (AMPS) in urine were isolated according to the method described by Dorfman and Matalon [9] using gel chromatography with Sephadex G-25. This was followed by precipitation of the AMPS fraction with dropwise addition of cetylpyridinium chloride. Care was taken not to add excessive amounts of cetylpyridinium chloride, since keratan sulfate and some heparan sulfate may be redissolved. Therefore, the supernatant fluid was reprecipitated with 6 vol of ethanol, electrophoresed, and -analyzed for the presence of AMPS. The AMPS-cetylpyridinium complex was dissolved in 2 M lithium chloride and the AMPS reprecipitated with 4 vol of ethanol. The precipitate was dried with ethanol and ether and then dissolved with water and used for electrophoresis and further studies. The analytical methods included the determination of uronic acid by the carbazole method of Dische [10]. Hexosamine was determined by the Boas modification of the Elson-Morgan method [11]. Total sulfate content was estimated by Muir's modification of the Dodgson and Spencer technique [12]. Carbohydrates were determined by the phenol method [13], and N-sulfated hexosamine was determined by the nitrous acid reaction as described by Lagunoff and Warren [14]. Electrophoresis of AMPS was performed on cellulose polyacetate strips (sepraphore III) as described by Matalon and Dorfman [15]. The latter technique permits quick screening for both the presence of AMPS and their electrophoretic mobility. Using these methods AMPS were isolated from two urine samples of the proband and two from her mother. From 24-hr urine samples of the proband, 30.8 mg and 19.8 mg AMPS were isolated. These amounts are excessive, since normal controls
KNIEST SYNDROME
759
a
b
d
FIG. 4.-Radiographs of proband (a-c) and mother (d). a, Lateral radiograph of mid- and
lower-thoracic spine. Note severe kyphosis with apex at T6 which is wedged anteriorly (arrow); vertebral bodies are flattened, irregular, and increased in anteroposterior diameters. b, Frontal radiograph of right ankle. Note irregular ossification on both sides of tibial and fibular epiphyseal plates and amorphously increased density in metaphyseal regions and osteoporosis of epiphyses and diaphyses. c, Radiograph of left hip. Femoral capital epiphysis is extremely flattened. Note coxa vara with shortening and thickening of femoral neck; acetabulum is irregular and hip joint space narrowed. d, Lateral radiograph of skull and upper cervical spine of mother. Sella turcica is small; odontoid process of second cervical vertebra (black arrow) is increased in anteroposterior diameter; decrease in height of body of third cervical vertebra (white arrow).
760
KIM ET AL.
of the same age yield less than 10 mg/24 hr. Considering the weight of the proband (22 kg), normal urines should seldom exceed 5 mg/24 hr. From two 24-hr urine samples of the mother, 18.6 mg and 15.2 mg AMPS were isolated. These amounts are also excessive, since normal controls for the same age have not exceeded 4-5 mg/24 hr. Electrophoresis of the AMPS excreted by the proband and her mother revealed mobility similar to standard keratan sulfate (gift of Dr. J. A. Cifonelli). The ratios of uronic acid to hexosamine were less than one in all samples: in the proband's urine they were 0.75 and 0.65, and in the mother, 0.40 and 0.48. These ratios are compatible with keratan sulfate but also with dermatan sulfate. Thus purification of the material isolated and further identification had to be carried out. In order to detect the presence of dermatan sulfate, which may give a low carbazole:hexosamine ratio, the material was treated with CuSO4 for precipitation of dermatan sulfate [16]. Only about 1.5%o of the material precipitated, while the bulk remained in the supernatant. The supernatant can include chondroitin 4/6sulfate, keratan sulfate, and heparan sulfate. We were unable to detect N-sulfated hexosamine, which is specific for heparin sulfate (and heparin), thus ruling out the presence of heparan sulfate. When the AMPS were subjected to chondroitinase ABC and then chromatographed on Sephadex G-25 [17], 94%o of the material was eluted in the void volume indicating nonsusceptibility to chondroitinase ABC, while only 6%o was included in the dissaccharide region. The elution pattern from Dowex 1, X 2 Clwas further examined and found to be characteristic of keratan sulfate since the major fraction was eluted with 4.0 M NaCl. The sulfate content of this fraction was determined; the SO4:hexosamine ratio was 1.02 for the proband and 1.03 for the mother. The uronic:hexosamine ratio in this fraction was 0.25, further indicating a pattern typical of keratan sulfate. These data indicate that both the proband and her mother excrete excessive amounts of polysaccharide and that this material was indeed keratan sulfate. Cultured skin fibroblasts of both mother and proband were highly metachromatic. The lysosomal enzymes, arylsulfatase A and B, a-N-acetylhexosaminidase, a glucosidase, a galactosidase, a iduronidase, a mannosidase, a fucosidase, /8-Nacetylhexosaminidase, /8 galactosidase, P glucosidase, and /8 glucuronidase studied in cultured skin fibroblasts from the mother and daughter by standard methods [18, 19] or modifications [20] were normal. Deficiency of the lysosomal enzyme chondroitin sulfate N-acetylhexosamine sulfate sulfatase has been demonstrated in Morquio syndrome [21]. This enzyme also had normal activity in the mother's fibroblasts. DISCUSSION
The Kniest syndrome should be differentially diagnosed from other forms of short-trunk dwarfism, especially spondyloepiphyseal dysplasia congenita (SED), Morquio syndrome, and metatropic dwarfism. These four chondrodystrophies primarily involve the spine causing platyspondyly which leads to short-trunk dwarfism.
KNIEST SYNDROME
761
In all there is a varying degree of epiphyseal and metaphyseal involvement of the tubular bones. The skeletal manifestations are present at birth in SED, metatropic dwarfism, and probably in the Kniest syndrome. However, Morquio syndrome is only recognizable later in life. Both metatropic dwarfism and Kniest syndrome present with short limbs and a relatively long trunk in early infancy, while in late infancy kyphoscoliosis develops resulting in short-trunk dwarfism. In SED shorttrunk dwarfism is present at birth. The combination of radiographic findings seen in our cases is similar to that previously described in the Kniest syndrome [1-6]. Platyspondyly and vertebral irregularity, metaphyseal flaring, and irregular ossification on both sides of the epiphyseal plate have been recognized as outstanding features of this syndrome [5, 6]. Each of the present cases had an unusually small sella turcica, as did Kniest's original patient. In many respects the Kniest syndrome resembles SED. In SED [21], the most severe vertebral hypoplasia tends to be at the thoraco-lumbar junction, while in our patients the wedged vertebrae at the apex of the kyphosis were in the midthoracic spine. The shape of the thorax is broad in SED rather than narrowed superiorly as in our patients. The configuration of the pelvis and femoral head and neck is similar except for flattening of the acetabular roof in SED. Although the ends of the bones are not as bulbous in SED, dome-shaped metaphyses with central bulging into the epiphyses, as seen in our proband, have been described in SED. Abnormalities of carpal ossifications, especially affecting the proximal row as seen in the mother, may be present in both conditions. The large odontoid in our patients is of considerable interest as a possible differentiating feature. In a review of the literature, Spranger and Langer [22] found odontoid hypoplasia in all patients with SED who were over 1 year of age. Morquio syndrome, while exhibiting obvious abnormalities of the spine, pelvis, and long bones, differs somewhat from the present cases. The pelvis in Morquio syndrome shows supraacetabular constriction, coxa valga, and narrow femoral necks. The apex of the kyphosis tends to be near the thoraco-lumbar junction, and beaked vertebral bodies are seen. The hands of the present cases show no tendency to the proximal metacarpal pointing of Morquio syndrome. Again, as in SED, the odontoid is hypoplastic. In Morquio syndrome, the lumbar bodies tend to be more severely affected than the thoracic. The reverse was true in the present cases. Numerous other bone changes of Morquio disease were lacking [2]. The Kniest syndrome is radiographically quite similar to metatropic dwarfism. Both show vertebral abnormalities, but platyspondyly is more marked in metatropic dwarfism. In both conditions there may be caudal narrowing of interpedicular distances. The fibula is frequently long in metatropic dwarfism and was of normal length in our patients. While both types of dwarfism show dumbell-shaped long bones, the irregular ossification on both sides of the epiphyseal plate is characteristic of the Kniest syndrome, as is the squaring of the metacarpophalangeal joints and narrowing of the joint spaces of the hands. In our patients the iliac bones were small and without the characteristic crescent shape described in metatropic dwarf-
762
KIM ET AL,
ism. Neither the small sella turcica nor prominent odontoid are typical of metatropic dwarfism. Extraskeletal manifestations present in these disorders are helpful for the diagnosis of these entities. The Kniest and Morquio syndromes and SED all have characteristic facies, but the face appears normal in metatropic dwarfism. Myopia and retinal detachment are frequently observed in SED. Corneal clouding develops in Morquio syndrome, and myopia has been reported in the Kniest syndrome. The electroretinographic abnormalities in the mother and daughter are inconclusive for the retinal degenerative disease which can occur in several of the mucopolysaccharidoses [23]. Serial determinations will be required to detect an abnormal response beyond what can occur in myopic eyes. It should also be noted that the history of cataract in the mother at age 25, and even the presence of a well developed cataract at age 43 years, anticipates by several decades the usual appearance of acquired lens opacities not due to trauma or preexisting intraocular inflammation. The daughter does not show abnormalities of the crystalline lenses at this time. It is possible that these will appear later, but still at a relatively early age; if so, they may constitute another component of this syndrome. Frequent otitis media and hearing loss has been observed in both Morquio and Kniest syndromes. The deafness in both may be of conductive or sensory-neural origin. Urinary excretion of keratan sulfate is present in Morquio syndrome, but no excess of mucopolysaccharide has been found in SED or metatropic dwarfism. The finding of increased amounts of AMPS in the urine of both of our patients has not been previously reported in the Kniest syndrome. In addition, there is a specifically high level of keratan sulfate comprising over 90%o of the polysaccharides isolated. Considering that normal urine contains only trace amounts of keratan sulfate [24], it must be assumed that the finding of keratan sulfaturia in the two patients described is directly related to the genetic defect. However, the isolation of keratan sulfate from urine and its documentation should always be approached with caution. Therefore, a step by step approach to exclude other mucopolysaccharides or glycoproteins was undertaken. Amounts of keratan sulfate in urine should be correlated with age, since Linder et al. [25] have shown in 12 patients that keratan sulfate excretion declines with age. This may account for the lower levels of keratan sulfate in the mother's urine. Despite the keratan sulfaturia, our two patients were enzymatically different from Morquio syndrome. A deficiency of N-acetylhexosamine 6-sulfate sulfatase has been found in Morquio disease [21]. When fibroblasts from one of our patients were assayed for N-acetylhexosamine 6-sulfate sulfatase, they were found to possess normal levels. While some of the previously reported patients with the Kniest syndrome have not demonstrated elevated amounts of total AMPS in the urine, not all such patients have been tested. Our report makes it apparent that the Kniest syndrome may be heterogeneous, with some patients excreting large quantities of keratan sulfate. This group may represent a new mucopolysaccharidosis with dominant inheritance.
KNIEST SYNDROME
763
The mode of inheritance has been established in SED as autosomal dominant and in both Morquio syndrome and metatropic dwarfism as autosomal recessive. The cases of Kniest syndrome reported in the literature have generally been sporadic except for two patients, a mother and a daughter, studied by Maroteaux and Spranger [26]. These cases, together with ours, suggest a dominant mode of inheritance in at least some cases of Kniest syndrome. Since no male-to-male transmission has yet been reported, it is not known whether the mutant gene which causes the Kniest syndrome is on an autosome or the X chromosome. The mean paternal age in the eight cases reported so far was calculated as 28½/2 years [6]. In view of the pattern of dominant inheritance observed in our family and the recessive inheritance in Morquio syndrome (both with urinary keratan sulfate excretion), it may be hypothesized that while Morquio syndrome is caused by the deficiency of an enzyme responsible for the degradation of keratan sulfate [21], the cases of the Kniest syndrome reported here may be due to an inhibitor of this enzyme or a mutation in another regulatory gene affecting this pathway. SUMMARY
A mother and daughter with clinical and radiographic findings typical of the Kniest syndrome are reported. It is apparent that this syndrome is dominantly inherited and that sporadic cases may represent fresh mutations. Abnormally high keratan sulfate excretion was found, indicating that the Kniest syndrome is a mucopolysacchariduria. ACKNOWLEDGMENTS We thank Drs. J. Dorst and D. Rimoin for helpful discussions. 1. 2. 3. 4. 5. 6.
7. 8.
9.
REFERENCES KNIEST W: Zur Abgrenzung der dysostosis euchondralis von der chondrodystrophie. Z. Kinderheilkd 70:633-640, 1952 McKusIcK VA: Mucopolysaccharidosis IV, in Heritable Disorders of Connective Tissue, 4th ed, edited by McKusIcK VA, St. Louis, Mosby, 1972, pp 583-611 LAROSE JH, GAY BB: Metatropic dwarfism. Am J Roentgenol Radium Ther Nucl Med 106:156-161, 1969 SILVERMAN FN: Introduction: skeletal dysplasias. Birth Defects: Orig Art Ser 10(9) :ix-xiv, 1974 RIMOIN DL, HOLLISTER DW, SIGGERS P, SILBERBERG R, LACHMAN R, McALISTER W, KAUFMAN R, McKUsICK VA, DORST J: Clinical, radiographic, histologic and ultra structural definition of the Kniest syndrome (abstr.). Pediatr Res 7:348, 1973 SIGGERs D, RIMOIN D, DORST P, DOTY S, WILLIAMS B, HOLLISTER D, SILBERG R, CRANLEY R, KAUFMAN R, McKuSICK VA: The Kniest syndrome. Birth Defects: Orig Art Ser 10(9) :193-208, 1974 JACOBSON JH: Clinical Electroretinography. Springfield, Ill., Thomas, 1961, pp. 148151 KRILL AE: Hereditary Retinal and Choroidal Diseases, vol. 1. Hagerstown, Md., Harper & Row, 1972 DORFMAN A, MATALON R: The mucopolysaccharidoses, in The Metabolic Basis of Inherited Disease, 3d ed, edited by STANBURY JB, WYNGAARDEN JB, FREDRICKSON DS, New York, McGraw-Hill, 1972, pp 1218-1272
764
KIM ET AL.
10. DISCHE Z: A new specific color reaction for glucuronic acid. J Biol Chem 171:725730, 1947 11. BOAS NG: Method for the determination of hexosamines in tissues. J Biol Chem 204:553-563, 1953 12. MUIR H: The nature of the link between protein and carbohydrate of a chondroitin sulfate complex from hyaline cartilage. Biochem J 69:195-204, 1958 13. DUBOIS M, GILLES KA, HAMILTON JK, REBERS PA, SMITH F: Colorimetric method for determination of sugars and related substances. Anal Chem 28:350-356, 1956 14. LAGUNOFF D, WARREN G: Determination of 2-deoxy-2-sulfaminohexose content of mucopolysaccharides. Arch Biochem Biophys 99:396-400, 1962 15. MATALON R, DORFMAN A: Hurler's syndrome: biosynthesis of acid mucopolysaccharides in tissue culture. Proc Natl Acad Sci USA 56:1310-1316, 1966 16. CIFONELLI JA, LuDoWIEG J, DORFMAN A: Chemistry of 18-heparin (chondroitin sulfate B). J Biol Chem 233:541-545, 1958 17. ROBINSON HC, DORFMAN A: The sulfation of chondroitin sulfate in embryonic chick cartilage epiphyses. J Biol Chem 244:348-352, 1969 18. MATALON R, DORFMAN A: Hurler's syndrome: an a-L-iduronidase deficiency. Biochem Biophys Res Commun 47:959-964, 1972 19. WEISSMANN B, RoWIN G, MARSHALL J, FREIDERICI D: Mammalian a-acetylglucosaminidase: enzymic properties, tissue distribution and intercellular localization. Biochemistry 6:207-214, 1967 20. BERATIS NG, TURNER BM, WEISS R, HIRSCHHORN K: Arylsulfatase B deficiency in Maroteaux-Lamy syndrome. Pediatr Res 9:475-480, 1975 21. MATALON R, ARBOGAST B, DORFMAN A: Morquio's syndrome: a deficiency of chondroitin sulfatase N-acetylhexosamine sulfate sulfatase. Biochem Biophys Res Commun 61:759-765, 1974 22. SPRANGER JW, LANGER LO: Sponylo-epiphyseal dysplasia congenita. Radiology 94: 313-322, 1970 23. GILLS JP, HOBSON R, HANLEY WB, MCKUSICK VA: Electroretinography and fundus oculi findings on Hurler's diseases and allied mucopolysaccharidosis. Arch Ophthalmol 74:596-603, 1965 24. VARADI DP, CIFONELLI JA, DORFMAN A: The acid mucopolysaccharides in normal urine. Biochim Biophys Acta 141:103-117, 1967 25. LINKER A, EVANS LR, MADSEN JA: Problems in the analysis of urinary mucopolysaccharide excretion. Biochem Med 2 :448-456, 1969 26. MAROTEAUX P, SPRANGER J : La maladie de Kniest. Arch Fr Pediatr 30:735-750, 1973
