Indian J Pediatr DOI 10.1007/s12098-014-1582-5
CLINICAL BRIEF
Novel Mutation and White Matter Involvement in an Indian Child with Pycnodysostosis Ankur Singh & Sergio Cuevas-Covarrubias & Gaurav Pradhan & V. K. Gautam & Olga Messina-Baas & Luz Maria Gonzalez-Huerta & Manisha Goyal & Seema Kapoor
Received: 20 November 2013 / Accepted: 1 September 2014 # Dr. K C Chaudhuri Foundation 2014
Abstract Pycnodysostosis (OMIM # 265800) is an inherited lysosomal disorder due to affection of cathepsin K gene, localised to 1q21. Pycnodysostosis can present with both skeletal and extraskeletal features. The index patient presented with cardinal features of short stature, dental and digital anomalies with history of multiple fractures. He, in addition had an unreported finding of white matter hyperintensity suggesting dysmyelination on neuroimaging. Molecular analysis revealed a homozygous insertion of single nucleotide in exon 5 of the CTSK gene that produces the substitution of phenylalanine instead of leucine at position 160 of protein and a premature termination of protein synthesis due to insertion of a stop codon. This mutation (c.480_481insT), (p.L160fsX173) is a novel frameshift mutation. The index
A. Singh Department of Pediatrics, LHMC and associated Kalawati Saran Children Hospital, New Delhi, India S. Cuevas-Covarrubias : O. Messina-Baas : L. M. Gonzalez-Huerta Department of Genetics, General Hospital of México, UNAM, Mexico City, Mexico G. Pradhan Department of Radiology, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India V. K. Gautam Department of Orthopedics, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India M. Goyal : S. Kapoor Division of Genetics, Department of Pediatrics, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India S. Kapoor (*) M-439, Ground Floor, Guruharkishan Nagar, Paschim Vihar, New Delhi 110087, India e-mail: [email protected]
case extends the phenotypic spectrum and the list of previously reported mutations in the CTSK gene. Keywords Pycnodysostosis . CTSK gene . Frameshift mutation
Introduction Pycnodysostosis (OMIM # 265800) is an autosomal recessive skeletal dysplasia, characterised by osteosclerosis, open fontanelles, acro-osteolysis, frequent fractures, obtuse angle mandible, parrot beak nose, grooved nails, hypodontia and extraskeletal manifestations. The disorder was first described by Maroteaux and Lamy in the year 1962 [1]. Porencephalic cyst has been previously reported in a child with pycnodysostosis but seizures with evidence of dysmyelination have not been reported [2]. The authors report an Indian case confirmed by sequencing to have a novel mutation and additional neuroimaging finding.
Case Report A 13-y-old boy was referred for evaluation of recurrent fractures and dysmorphology. The child was product of third degree consanguineous marriage, born at home after uneventful perinatal period. The child was normal till first year of age, when he had his first fracture of right sided clavicle after trivial injury; subsequently he had multiple episodes of bony fractures of long bones of lower limb. All the fractures were preceded by very trivial trauma. There was delayed eruption of deciduous and permanent teeth but his dental examination was normal. He also had history of generalised tonic clonic seizures for last 2 y. Currently, his scholastic performance is
Indian J Pediatr
Fig 1 Radiographs bilateral hands showing acrosteolysis of terminal phalanges
average with IQ score of 85. His anthropometric parameters (weight : 33 kg; 0 & +2 z scores) were normal except for disproportionate short stature (height : 125 cm US/LS : 1.27). His neurological examination was essentially normal. Dysmorphology assessment revealed flat forehead, patent fontanelles (anterior and posterior), long and beaked nose, micrognathia, short and stubby fingers, grooved and flattened finger and toe nails. Orthopedic consultation revealed fracture shaft of the right femur. Radiographic examination of long bones revealed increased bone density with loss of corticomedullary differentiation with closed fracture of right mid shaft of femur. Skull and face radiography showed open anterior and posterior sutures with complete loss of mandibular angle. Radiograph of bilateral hands showed acrosteolysis of terminal phalanges (Fig. 1). Neuroimaging of the brain showed symmetrical areas of hypodensity in fronto-temporal areas (Fig. 2). EEG was normal. Biochemical parameters (calcium, phosphate, alkaline phosphatase) and anti measles antibody in serum and CSF were within normal limits. Enzyme levels of arylsulfatase, galactocerobosidase, very long chain fatty acids and both tandem mass spectrometry and gas chromatography were essentialy normal. DNA sequencing analysis revealed a (c.480_481insT), (p.L160fsX173) frameshift homozygous mutation in proband whereas the
Fig 2 (A) CT scan showing hypo densities in the white matter in bilateral frontal area (marked by arrow), and in the (B) temporal area. (marked by arrow)
parents had heterozygous mutation of the same (Fig. 3) . It resulted in the substitution of leucine at position 160 by phenylalanine (L160F) in the middle portion of the CTSK gene and in a premature stop codon (p.L160fsX173). No similar change in the CTSK gene was present in 100 normal controls. Discussion Pycnodysostosis is a rare, autosomal recessive sclerosing skeletal dysplasia, caused by cathepsin K deficiency and is suggested to be included as a lysosomal storage disorder. Diagnosis was established in the proband based on presence of major clinical (open anterior fontanel, dolicocephaly, small face, receding chin, hypoplastic maxilla, parrot beak nose, wide mandibular angle and increased bone fragility) and major radiological (persistence of anterior/posterior fontanel, obtuse angle of mandible, generalised osteosclerosis and osteolysis of distal phalanges) features. Pycnodysostosis was first reported
Indian J Pediatr Fig 3 Proband chromatogram showing substitution of leucine at position 160 by phenylalanine (L160F) (shown by arrow)
from India by Chawla in 1964; since then clinical cases have been reported, highlighting the dysmorphology, unusual association, surgical aspects related to orthopedics and anesthesia [3–8]. The index case, in addition had seizures with no significant perinatal history and the presence of symmetrical areas of hypodensity in frontotemporal area on neuroimaging suggestive of dysmyelination. Possible causes that were included in work up for dysmyelination were: Subacute sclerosing panencephalitis, leucocystrophies, (Metachromatic Leucodystrophy, Krabbe, Adrenoleucodystrophy, organic academia). All results were negative. Probability that Cathepsin K deficiency might involve brain, like other lysosomal disorders, is suggested. Porencephalic cyst has been previously reported with a probable etiology being referred to as faulty anatomical relationship between brain growth and vascular supply [2]. But in isolation the authors admit this is just a postulate and functional studies would be required to substantiate this. Differential diagnosis includes osteopetrosis and cleidocranial dysplasia. Presence of open anterior/posterior fontanel and obtuse mandibular angle ruled out osteopetrosis while presence of normal clavicle and increased bone density ruled out cleidocranial dysplasia. Short stature is usually present in pycnodysostosis and has important treatment implications as it is thought to be associated with low IGF1 levels. GH therapy can increase IGF-I secretion and improve linear growth and therefore, was proposed as a treatment modality [9]. Mutation in CTSK gene results in failure to degrade organic matrix leading to generalised osteosclerosis. In the present study the authors describe a novel homozygous insertion of single nucleotide in exon 5 of CTSK gene. This resulted in truncated, dysfunctional protein and in manifestation of the disease in the present case. The first mutation in Indian family was reported by Hou et al. in year 1999. It was a missense (c.830C>A; p A277E) homozygous mutation, located in exon 7 of the CTSK gene, a mutational hot spot for Pycnodysostosis [10]. The present report, highlights the variability in existence of genotype, despite the availability of two mutational hot spots Arg241 (exon6), Ala277 (exon 7) and also adds to its phenotypic spectrum [10]. The neuroimaging finding
needs to be further substantiated by more cases and functional studies to identify the role of cathepsin K in central nervous system.
Contributions AS was involved in clinical case management and drafting the manuscript and is the first author. SC-C, OM-B, LMG-H were involved in mutation analysis and interpretation of result. GP made the radiological diagnosis. VKG was involved in orthopedic management of the case. MG did literatutre search regarding the manuscript. SK critically reviewed the manuscript made the diagnosis and will act as guarantor for the manuscript. Conflict of Interest None. Source of Funding None.
References 1. Maroteaux P, Lamy M. Pyknodysostosis. Presse Med. 1962;70:999– 1002. 2. Figueiredo J, Reis A, Vaz R, Leáo M, Cruz C. Porencephalic cyst in pycnodysostosis. J Med Genet. 1989;26:782–4. 3. Mujawar Q, Naganoor R, Patil H, Thobbi AN, Ukkali S, Malagi N. Pycnodysostosis with unusual findings: a case report. Cases J. 2009;2:6544. doi:10.4076/1757–1626–2–6544. 4. Chawla S. Cranio-skeletal dysplasia with acro-osteolysis. Br J Radiol. 1964;37:702–5. 5. Kumar R, Misra PK, Singhal R. An unusual case of pycnodysostosis. Arch Dis Child. 1988;63:558–9. 6. Kundu ZS, Marya KM, Devgan A, Yadav V, Rohilla S. Subtrochanteric fracture managed by intramedullary nail in a patient with pycnodysostosis. Joint Bone Spine. 2004;71:154–6. 7. Kshirsagar VY, Ahmed M, Nagarsenkar S, Sahoo K, Shah KB. Ichthyosis vulgaris and pycnodysostosis: an unusual occurrence. Acta Med Acad. 2012;41:214–8. 8. Puri R, Saxena A, Mittal A, Arshad Z, Dwivedi Y, Chand T, et al. Pycnodysostosis: an anaesthetic approach to this rare genetic disorder. Case Rep Anesthesiol. 2013;2013:716756. doi:10.1155/2013/ 716756. Epub 2013 Mar 14. 9. Rothenbühler A, Piquard C, Gueorguieva I, Lahlou N, Linglart A, Bougnères P. Near normalization of adult height and body proportions by growth hormone in pycnodysostosis. J Clin Endocrinol Metab. 2010;95:2827–31. 10. Hou WS, Brömme D, Zhao Y, Mehler E, Dushey C, Weinstein H. Characterization of novel cathepsin K mutations in the pro and mature polypeptide regions causing pycnodysostosis. J Clin Invest. 1999;103:731–8.
CLINICAL BRIEF
Novel Mutation and White Matter Involvement in an Indian Child with Pycnodysostosis Ankur Singh & Sergio Cuevas-Covarrubias & Gaurav Pradhan & V. K. Gautam & Olga Messina-Baas & Luz Maria Gonzalez-Huerta & Manisha Goyal & Seema Kapoor
Received: 20 November 2013 / Accepted: 1 September 2014 # Dr. K C Chaudhuri Foundation 2014
Abstract Pycnodysostosis (OMIM # 265800) is an inherited lysosomal disorder due to affection of cathepsin K gene, localised to 1q21. Pycnodysostosis can present with both skeletal and extraskeletal features. The index patient presented with cardinal features of short stature, dental and digital anomalies with history of multiple fractures. He, in addition had an unreported finding of white matter hyperintensity suggesting dysmyelination on neuroimaging. Molecular analysis revealed a homozygous insertion of single nucleotide in exon 5 of the CTSK gene that produces the substitution of phenylalanine instead of leucine at position 160 of protein and a premature termination of protein synthesis due to insertion of a stop codon. This mutation (c.480_481insT), (p.L160fsX173) is a novel frameshift mutation. The index
A. Singh Department of Pediatrics, LHMC and associated Kalawati Saran Children Hospital, New Delhi, India S. Cuevas-Covarrubias : O. Messina-Baas : L. M. Gonzalez-Huerta Department of Genetics, General Hospital of México, UNAM, Mexico City, Mexico G. Pradhan Department of Radiology, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India V. K. Gautam Department of Orthopedics, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India M. Goyal : S. Kapoor Division of Genetics, Department of Pediatrics, Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India S. Kapoor (*) M-439, Ground Floor, Guruharkishan Nagar, Paschim Vihar, New Delhi 110087, India e-mail: [email protected]
case extends the phenotypic spectrum and the list of previously reported mutations in the CTSK gene. Keywords Pycnodysostosis . CTSK gene . Frameshift mutation
Introduction Pycnodysostosis (OMIM # 265800) is an autosomal recessive skeletal dysplasia, characterised by osteosclerosis, open fontanelles, acro-osteolysis, frequent fractures, obtuse angle mandible, parrot beak nose, grooved nails, hypodontia and extraskeletal manifestations. The disorder was first described by Maroteaux and Lamy in the year 1962 [1]. Porencephalic cyst has been previously reported in a child with pycnodysostosis but seizures with evidence of dysmyelination have not been reported [2]. The authors report an Indian case confirmed by sequencing to have a novel mutation and additional neuroimaging finding.
Case Report A 13-y-old boy was referred for evaluation of recurrent fractures and dysmorphology. The child was product of third degree consanguineous marriage, born at home after uneventful perinatal period. The child was normal till first year of age, when he had his first fracture of right sided clavicle after trivial injury; subsequently he had multiple episodes of bony fractures of long bones of lower limb. All the fractures were preceded by very trivial trauma. There was delayed eruption of deciduous and permanent teeth but his dental examination was normal. He also had history of generalised tonic clonic seizures for last 2 y. Currently, his scholastic performance is
Indian J Pediatr
Fig 1 Radiographs bilateral hands showing acrosteolysis of terminal phalanges
average with IQ score of 85. His anthropometric parameters (weight : 33 kg; 0 & +2 z scores) were normal except for disproportionate short stature (height : 125 cm US/LS : 1.27). His neurological examination was essentially normal. Dysmorphology assessment revealed flat forehead, patent fontanelles (anterior and posterior), long and beaked nose, micrognathia, short and stubby fingers, grooved and flattened finger and toe nails. Orthopedic consultation revealed fracture shaft of the right femur. Radiographic examination of long bones revealed increased bone density with loss of corticomedullary differentiation with closed fracture of right mid shaft of femur. Skull and face radiography showed open anterior and posterior sutures with complete loss of mandibular angle. Radiograph of bilateral hands showed acrosteolysis of terminal phalanges (Fig. 1). Neuroimaging of the brain showed symmetrical areas of hypodensity in fronto-temporal areas (Fig. 2). EEG was normal. Biochemical parameters (calcium, phosphate, alkaline phosphatase) and anti measles antibody in serum and CSF were within normal limits. Enzyme levels of arylsulfatase, galactocerobosidase, very long chain fatty acids and both tandem mass spectrometry and gas chromatography were essentialy normal. DNA sequencing analysis revealed a (c.480_481insT), (p.L160fsX173) frameshift homozygous mutation in proband whereas the
Fig 2 (A) CT scan showing hypo densities in the white matter in bilateral frontal area (marked by arrow), and in the (B) temporal area. (marked by arrow)
parents had heterozygous mutation of the same (Fig. 3) . It resulted in the substitution of leucine at position 160 by phenylalanine (L160F) in the middle portion of the CTSK gene and in a premature stop codon (p.L160fsX173). No similar change in the CTSK gene was present in 100 normal controls. Discussion Pycnodysostosis is a rare, autosomal recessive sclerosing skeletal dysplasia, caused by cathepsin K deficiency and is suggested to be included as a lysosomal storage disorder. Diagnosis was established in the proband based on presence of major clinical (open anterior fontanel, dolicocephaly, small face, receding chin, hypoplastic maxilla, parrot beak nose, wide mandibular angle and increased bone fragility) and major radiological (persistence of anterior/posterior fontanel, obtuse angle of mandible, generalised osteosclerosis and osteolysis of distal phalanges) features. Pycnodysostosis was first reported
Indian J Pediatr Fig 3 Proband chromatogram showing substitution of leucine at position 160 by phenylalanine (L160F) (shown by arrow)
from India by Chawla in 1964; since then clinical cases have been reported, highlighting the dysmorphology, unusual association, surgical aspects related to orthopedics and anesthesia [3–8]. The index case, in addition had seizures with no significant perinatal history and the presence of symmetrical areas of hypodensity in frontotemporal area on neuroimaging suggestive of dysmyelination. Possible causes that were included in work up for dysmyelination were: Subacute sclerosing panencephalitis, leucocystrophies, (Metachromatic Leucodystrophy, Krabbe, Adrenoleucodystrophy, organic academia). All results were negative. Probability that Cathepsin K deficiency might involve brain, like other lysosomal disorders, is suggested. Porencephalic cyst has been previously reported with a probable etiology being referred to as faulty anatomical relationship between brain growth and vascular supply [2]. But in isolation the authors admit this is just a postulate and functional studies would be required to substantiate this. Differential diagnosis includes osteopetrosis and cleidocranial dysplasia. Presence of open anterior/posterior fontanel and obtuse mandibular angle ruled out osteopetrosis while presence of normal clavicle and increased bone density ruled out cleidocranial dysplasia. Short stature is usually present in pycnodysostosis and has important treatment implications as it is thought to be associated with low IGF1 levels. GH therapy can increase IGF-I secretion and improve linear growth and therefore, was proposed as a treatment modality [9]. Mutation in CTSK gene results in failure to degrade organic matrix leading to generalised osteosclerosis. In the present study the authors describe a novel homozygous insertion of single nucleotide in exon 5 of CTSK gene. This resulted in truncated, dysfunctional protein and in manifestation of the disease in the present case. The first mutation in Indian family was reported by Hou et al. in year 1999. It was a missense (c.830C>A; p A277E) homozygous mutation, located in exon 7 of the CTSK gene, a mutational hot spot for Pycnodysostosis [10]. The present report, highlights the variability in existence of genotype, despite the availability of two mutational hot spots Arg241 (exon6), Ala277 (exon 7) and also adds to its phenotypic spectrum [10]. The neuroimaging finding
needs to be further substantiated by more cases and functional studies to identify the role of cathepsin K in central nervous system.
Contributions AS was involved in clinical case management and drafting the manuscript and is the first author. SC-C, OM-B, LMG-H were involved in mutation analysis and interpretation of result. GP made the radiological diagnosis. VKG was involved in orthopedic management of the case. MG did literatutre search regarding the manuscript. SK critically reviewed the manuscript made the diagnosis and will act as guarantor for the manuscript. Conflict of Interest None. Source of Funding None.
References 1. Maroteaux P, Lamy M. Pyknodysostosis. Presse Med. 1962;70:999– 1002. 2. Figueiredo J, Reis A, Vaz R, Leáo M, Cruz C. Porencephalic cyst in pycnodysostosis. J Med Genet. 1989;26:782–4. 3. Mujawar Q, Naganoor R, Patil H, Thobbi AN, Ukkali S, Malagi N. Pycnodysostosis with unusual findings: a case report. Cases J. 2009;2:6544. doi:10.4076/1757–1626–2–6544. 4. Chawla S. Cranio-skeletal dysplasia with acro-osteolysis. Br J Radiol. 1964;37:702–5. 5. Kumar R, Misra PK, Singhal R. An unusual case of pycnodysostosis. Arch Dis Child. 1988;63:558–9. 6. Kundu ZS, Marya KM, Devgan A, Yadav V, Rohilla S. Subtrochanteric fracture managed by intramedullary nail in a patient with pycnodysostosis. Joint Bone Spine. 2004;71:154–6. 7. Kshirsagar VY, Ahmed M, Nagarsenkar S, Sahoo K, Shah KB. Ichthyosis vulgaris and pycnodysostosis: an unusual occurrence. Acta Med Acad. 2012;41:214–8. 8. Puri R, Saxena A, Mittal A, Arshad Z, Dwivedi Y, Chand T, et al. Pycnodysostosis: an anaesthetic approach to this rare genetic disorder. Case Rep Anesthesiol. 2013;2013:716756. doi:10.1155/2013/ 716756. Epub 2013 Mar 14. 9. Rothenbühler A, Piquard C, Gueorguieva I, Lahlou N, Linglart A, Bougnères P. Near normalization of adult height and body proportions by growth hormone in pycnodysostosis. J Clin Endocrinol Metab. 2010;95:2827–31. 10. Hou WS, Brömme D, Zhao Y, Mehler E, Dushey C, Weinstein H. Characterization of novel cathepsin K mutations in the pro and mature polypeptide regions causing pycnodysostosis. J Clin Invest. 1999;103:731–8.
