Eur J Pediatr (1992) 151 : 117-120

EuropeanJournal of

Pediatrics

9 Springer-Verlag1992

Clinical recognition of patients affected by a peroxisomal disorder: a retrospective study in 40 patients A. C. Theil, R. B. H. Schutgens, R . J . A . Wanders, and H. S. A. Heymans Department of Paediatrics, Universityof Amsterdam, AMC, 9 Meibergdreef, NL-1105 AZ Amsterdam,The Netherlands Received April 17, 1990 / Accepted after revision June 4, 1991

Abstract. Peroxisomal disorders are genetic diseases in which an impairment in one or more peroxisomal function(s) causes clinical and multiple biochemical abnormalities. Early recognition of the major peroxisomal disorders in which functional peroxisomes are virtually absent, leading to a generalised impairment of peroxisomal functions, is of utmost importance, as this will enable the prenatal diagnosis of these severe diseases in future pregnancies. Unfortunately, clinical recognition of these disorders can be difficult because of the aspecific and varying phenotypic presentation. We analysed the clinical characteristics in 40 patients suspected of having a peroxisomal disorder to identify specific clinical criteria for diagnosis. From this study we conclude that the combined presence of at least three major clinical characteristics (present in > 75% of the affected patients, including psychomotor retardation, hypotonia, impaired hearing, low/broad nasal bridge, abnormal ERG, hepatomegaly) and one or more minor characteristics (present in 50%-75% of the patients, like large fontanelles, shallow orbital ridges, epicanthus, anteverted nostrils, retinitis pigmentosa) warrants biochemical investigation of peroxisomal functions. Further prospective investigations will have to be done to evaluate these criteria. Key words: Peroxisomal disorder - Zellweger syndrome - Peroxisomes

Introduction In the early 1960s two groups of clinicians independently described an extraordinary combination of clinical and pathological-anatomical abnormalities in six patients. A few years later, this entity became known as the cerebrohepato-renal syndrome of Zellweger (ZS). In subsequent Offprint requests to: H. S. A. Heymans,Department of Paediatrics, Universityof Groningen,Postbus 30001, NL-9700 RB Groningen, The Netherlands Abbreviations: PDD = peroxisomedeficiencydisorders; RCDP

= rhizomelic type of chondrodysplasia punctata; ZS = Zellweger syndrome

years, at least 150 children with a similar clinical presentation were described. Common clinical characteristics include a typical cranio-facial appearance, severe hypotonia, severe psychomotor retardation, renal cysts, liver function disturbances, and failure to thrive. Most children suffering from this autosomal recessive disease die within the first 6 months of life [see reviews 9, 12, 13, 15, 21]. The first step towards understanding the biochemical basis of this syndrome was taken in 1973 by Goldfischer and co-workers [6]. In ultrastructural studies they found that peroxisomes were not morphologically detectable in hepatocytes and renal tubule cells from ZS patients, although recent results suggest that aberrant peroxisomal structures are present in Zellweger cells which are devoid of most peroxisomal enzyme proteins and hence functionally inactive [see 12 and 21 for discussion]. The impact of this finding was not immediately recognised since at that time knowledge concerning functions of peroxisomes in mammalian cells was rather limited. At present we know that in humans peroxisomes are not only involved in hydrogen peroxide metabolism [5], but also play an essential role in the [3-oxidation of very long chain fatty acids, in the biosynthesis of bile acids, and etherphospholipids, in the metabolism of pipecolic acid and probably phytanic acid, and other metabolic processes. Recently other genetic disorders were recognised as sharing some of the clinical and/or biochemical characteristics of ZS. We now recognise 13 different diseases which belong to the group of peroxisomal disorders. On biochemical grounds these disorders can be divided into three groups (Table 1). Group 1, disorders characterised by a virtually complete loss of peroxisomes and peroxisomal functions are called the peroxisome deficiency disorders (PDD [21], alternatively called disorders of peroxisome biogenesis [12]), ZS, infantile Refsum disease, neonatal adrenoleukodystrophy, and hyperpipecolic acidaemia belong to this group. Group 2, characterised by the loss of two or more peroxisomal functions, includes the rhizomelic type of chondrodysplasia punctata (RCDP) [10, 11, 17] and the "Zellweger-like syndrome" [20]. Group 3 is characterised by the loss of only a single peroxisomal function, consists of X-linked adrenoleukodystrophy, peroxisomal acyl-CoA oxidase deficiency [14],

118 Table 1. Classification of peroxisomal disorders

Enzyme defect A.

Generalised loss of peroxisomal functions Cerebro-hepato-renal (Zellweger syndrome) Neonatal adrenoleukodystrophy Infantile Refsum disease Hyperpipecolic acidaemia

Generalised Generalised Generalised Generalised

B. Loss of multiple peroxisomal functions Rhizomelie chondrodysplasia punctata Zellweger-like syndrome

DHAP-AT, alkyl DHAP synthase, phytanic acid oxidase DHAP-AT, peroxisomal [~-oxidation enzyme proteins

C. Loss of a single peroxisomal function Adrenoleukodystrophy/Adrenomyeloneuropathy Acyl-CoA oxidase deficiency (pseudo-NALD) Bifunctional protein deficiency Thiolase deficiency (pseudo-Zellweger syndrome) Hyperoxaluria type I Acatalasaemia Adult Refsum disease

Peroxisomal VLCFA-CoA synthetase Acyl-CoA oxidase Bifunctional enzyme Peroxisomal thiolase Alanine: glyoxylate aminotransferase Catalase Phytanic acid oxidase

DHAP-AT, Dihydroxyacetonephosphate-acyltransferase;

NALD, neonatal adrenoleukodystrophy; VLCFA, very long chain fatty acids

bifunctional enzyme deficiency [22], peroxisomal thiolase deficiency (pseudo-ZS) [7], hyperoxaluria type I [4] and acatalasaemia. W h e t h e r the adult type of Refsum disease is also a peroxisomal disorder has still to be established. As m o r e biochemical p a r a m e t e r s became available for the diagnosis of the different peroxisomal disorders, it also became clear that in m a n y patients the clinical presentation is often aspecific, showing a wide divergence in phenotypic expression which strongly depends upon the patient's age [1, 3, 9]. Moreover, in some peroxisomal disorders (like in P D D ) , the clinical presentation changes with age [2]. F r o m the literature it can be concluded that in P D D , severe hypotonia is the most striking clinical feature in the first days of life, whereas in the following period up to the 12th month of life, cranio-facial dysm o r p h i s m becomes m o r e apparent. After this period the clinical presentation seems to be more aspecific, but is dominated by severe psychomotor retardation in all patients [8, 9, 12]. In our study, we have attempted to compose a list of clinical selection criteria, on the basis of which clinicians will be able to pre-select patients in w h o m biochemical investigations aimed at identifying an impairment in one or m o r e peroxisomal function(s) should be carried out.

Methods

Making use of a literature study of patients affected by either a PDD or RCDP [10], a questionnaire was composed consisting of 115 items concerning their different clinical, biochemical, roentgenological, pathological-anatomical and epidemiological characteristics. Each item could be scored with present (+) or absent (-), or no information available (0). No specific attention was paid to the age at which the information was gathered. The questionnaire was sent to physicians of 80 patients, suspected of a peroxisomal disorder by their clinical resemblance to previously described pa-

tients with a peroxisomal disorder. From these patients, blood, fibroblasts and/or tissue samples were investigated biochemically by us during the period 1984-1987. Biochemical investigations included the analysis of "de novo" plasmalogen biosynthesis in fibroblasts, measurements of the activity of acyl-CoA: dihydroxyacetonephosphate acyltransferase in fibroblasts and/or platelets, plasmalogen analysis in erythrocytes and/or fibroblasts, catalase latency in fibroblasts, and the analysis of plasma very long chain (> C22) fatty acids, phytanic acid and bile acids respectively [16, 21]. These analyses will demonstrate whether or not there is an impairment in one or more peroxisomal functions in a particular patient. In this study, the patients initially suspected to be affected by a peroxisomal disorder on clinical grounds only, but without a biochemically detectable dysfunction of peroxisomes, served as a "control" group. The choice of this group enabled us to select some useful specific criteria allowing clinical recognition of patients suffering from a peroxisomal disorder.

Results

Forty questionnaires were returned with sufficient information to be included in this study. According to the results of biochemical analyses, 28 of these 40 patients were affected by a peroxisomal disorders, whereas in the 12 remaining patients no peroxisomal dysfunction was found. The group of patients with a peroxisomal disorder analysed in this paper, consisted of 19 patients with a generalized loss of peroxisomal functions (PDD), 7 with R C D P , and 2 with a peroxisomal disorder due to a single peroxisomal defect (at the level of acyl-CoA oxidase and peroxisomal thiolase respectively). Psychom o t o r retardation was found to be present in all P D D cases studied. Major clinical characteristics, (defined as characteristics present in m o r e than 75% of the P D D patients) are low/broad nasal bridge, hypotonia, impaired hearing, abnormal E R G and hepatomegaly present in the 1st year of life. Minor characteristics of P D D , (defined as features present in 5 0 % - 7 5 % of the P D D pa-

119 Table 2. Comparison of the clinical characteristics of patients with a PDD, and a "control" group of patients initially suspected for a peroxisomal disorder in whom no biochemical support for this diagnosis was obtained

PDD (n = 19)

Major characteristics Psychomotor retardation Hypotonia Impaired hearing Low/broad nasal bridge Abnormal E.R.G. Hepatomegaly in 1st year

Numbera (%)b

Controls (n = 12) Numbera (%)b

16 / 16 18 / 19 9 / 12 12 / 16 7/ 8 12 / 15

(100) (95) (75) (75) (88) (80)

6/ 9 10 / 11 3/ 8 1/ 9 3/7 0/ 8

(67) (91) (38) (11) (43) (0)

10 / 18 10 / 16 7 / 14 8 / 15 8 / 15

(55) (63) (50) (54) (53)

0/ 8 0/8 0/ 9 1/ 9 1/ 8

(0) (0) (0) (11) (13)

Minor characteristics

Large fontanelles Shallow orbital ridges Epicantus Anteverted nostrils Retinitis pigmentosa

a Number of patients in which feature is present/total number of patients in the group in which information about the feature was present b % of cases in which the feature was present

in older patients varies with age. However, because methods for prenatal diagnosis are available [18, 19], early (clinical) recognition in particular of P D D , is mandatory. A list with specific clinical criteria could contribute to the early recognition of peroxisomal disorders. F r o m the data in Table 2 it can be concluded that patients affected by a P D D (group 1) present with psychom o t o r retardation, low/broad nasal bridge, hypotonia, impaired hearing, h e p a t o m e g a l y in the 1st year and an abnormal E R G . These major characteristics are found in m o r e than 75% of the patients affected by a P D D and are encountered mostly in a substantially lower percentage in the "control" population. Next to these characteristics the P D D patients m a y show large fontanelles, absent orbital ridges, epicanthus, anteverted nostrils and abnormal retinal pigmentation. These characteristics were reported in 5 0 % - 7 5 % of the P D D population. In contrast to the major characteristics, these minor characteristics were hardly encountered in the "control" population ( 0 % - 1 3 % ) . Comparison of these data between the P D D and our "control" population shows that some overlap in cinical characteristics occurs. This indicates that the clinical characteristics of P D D are not specific. Because the n u m b e r of patients involved in this study is too small to allow statistical analysis, we composed a list of clinical selection criteria that would have the greatest predictive diagnostic value, when applied to the population studied in this paper. Based on the evaluation of our data we would suggest that biochemical tests are warranted in any patient showing at least three of the m a j o r clinical characteristics and one of the minor characteristics. These clinical criteria need further examination in a prospective study.

tients), are large fontanelles, shallow orbital ridges, epicanthus, anteverted nostrils and retinitis pigmentosa (Table 2). With the exception of the item hepatomegaly in the 1st year of life, the major criteria were not only present in most cases of the peroxisomal disorders, but were also frequently found in the "control" population (between 1 1 % - 9 1 % ) . The minor clinical criteria however were only rarely seen in the "control" population. R C D P showed a different clinical pattern, with a substantially higher percentage of patients with a short stature, cataract, flexion contracture and other features.

Acknowledgements: We thank the following colleagues for their cooperation; J. Motte, M. Gautier, J. Scotto, Mrs. I. Zweije-Hofman, K. Bartlett, J. M. Connor, Mrs. E. M. Bleeker-Wagemakers, P. Aubourg, J. L. Ket, Mrs. P. D. Maaswinkel-Mooy, F. Skovby.

Discussion

References

In a retrospective study of 40 patients from w h o m blood and/or tissue samples were sent to our laboratory on the clinical suspicion of a peroxisomal disease, we tried to select those clinical features which could be valuable for clinical pre-selection of especially the P D D . Studying the clinical features of this group of peroxisomal disorders seems especially relevant since in some peroxisomal disorders including X-linked adre.noleukodystrophy, Refsum disease, acatalasaemia and hyperoxaluria type I, the combination of clinical symptoms is m o r e or less specific and distinct from P D D while others including peroxisomal acyl-CoA oxidase deficiency, pseudo-ZS and Zellweger-like syndrome show a m a r k e d overlap in clinical symptomatology with P D D allowing selection on the same clinical criteria. Clinical recognition of patients affected by a P D D can be difficult since most children die in the first 6 months of life and the clinical presentation

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