Cerebrotendinous xanthomatosis with predominant parkinsonian syndrome: further confirmation of the clinical heterogeneity

First case series of Polish patients with cerebrotendinous xanthomatosis and systematic review of cases from the 21st century

Cerebrotendinous xanthomatosis (CTX) is an inborn error of metabolism caused by recessive variants in the cytochrome P450 CYP27A1 gene. CTX is said to manifest with childhood-onset chronic diarrhea and the classic triad of juvenile-onset cataracts, Achilles tendons xanthomas, and progressive ataxia. It is currently one of the few inherited neurometabolic disorders amenable to a specific treatment. The diagnosis may be significantly delayed resulting in permanent neurological impairment. A retrospective review of the clinical characteristics and diagnostic findings in case series of six Polish patients with CTX. Additional retrospective review of symptoms and pathogenic variants of 568 CTX available cases and case series from the past 20 years. To the best of our knowledge, this is the widest review of CTX cases reported in years 2000-2021. We report the largest cohort of Polish patients ever published, with the identification of two hot-spot mutations. During the review of available 568 cases, we found significant differences in the clinical phenotypes and the localization of variants within the gene between Asian and non-Asian populations. These findings may facilitate molecular testing in the Polish and Asian populations. Invariably better screening for CTX and wider awareness is needed.

Movement disorders in cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is an inborn error of cholesterol and bile acid metabolism, leading to neuropsychiatric and systemic manifestations. Movement disorders have rarely been reported in CTX, while a detailed appreciation of the full phenotypic spectrum is required in order to prevent underdiagnosis of this disease. This review focuses on the frequency of more unusual, non-ataxia and non-spasticity movement disorders reported in CTX. In total, 39 articles were reviewed, describing 55 CTX patients with a movement disorder. Additionally, we report on seven patients with parkinsonism out of our Dutch cohort of 79 (77 genetically proven) CTX patients. Mean age at onset of the movement disorder was 40 ± 12 years (median 40, range 13-62 years). Movement disorders can be considered a late disease manifestation. Parkinsonism was the most frequently reported movement disorder, followed by dystonia, myoclonus and postural tremor. Movement disorders were found to be mixed in 23% of patients and were usually part of a complex clinical picture, rather than a prominent symptom. Still, in 18% of the cases, a movement disorder was the presenting symptom. Unusual movement disorders represent a rare clinical feature in CTX, but CTX should be considered in the differential diagnosis of these movement disorders, particularly in case of early onset, and when associated with other neurological features (especially cognitive impairment, pyramidal and cerebellar signs) and/or with systemic features (such as diarrhoea, cataract and tendon xanthomas). CTX is a treatable disorder, stressing the importance of considering CTX as a potential cause of movement disorders.

Sterol 27-Hydroxylase Polymorphism Significantly Associates With Shorter Telomere, Higher Cardiovascular and Type-2 Diabetes Risk in Obese Subjects

BACKGROUND/OBJECTIVES

The pathologic relationship linking obesity and lipid dismetabolism with earlier onset of aging-related disorders, including cardiovascular disease (CVD) and type-2 diabetes (T2D), is not fully elucidate. Chronic inflammatory state, in obese individuals, may accelerate cellular aging. However, leukocyte telomere length (LTL), the cellular biological aging indicator, is elusively linked with obesity. Recent studies indicate that sterol 27-hydroxylase (CYP27A1) is an emerging antiatherogenic enzyme, that, by converting extrahepatic cholesterol to 27-hydroxycholesterol, facilitates cholesterol removal via high-density lipoprotein-cholesterol (HDL-C). We tested the hypothesis that obese subjects who carry at least three copies of CYP27A1 low-hydroxylation (LH) activity genome-wide-validated alleles (rs4674345A, rs1554622A, and rs4674338G) present premature aging, as reflected in shorter LTL and higher levels of CVD/T2D risk factors, including reduced HDL-C.

SUBJECTS/METHODS

Obese subjects from SPHERE project {n = 1,457; overweight [body mass index (BMI) 25-30 kg/m²] 65.8% and severe-obese (BMI > 30 kg/m²) 34.2%} were characterized for the presence from 0 to 6 LH-CYP27A1 allele copy number. Univariate and multivariable sex-age-smoking-adjusted linear-regression models were performed to compare CVD/T2D risk factors and biological aging (LTL) in relation to the combined BMI-LH groups: overweight-LH: 0-2, overweight-LH: 3-6, severe-obese-LH: 0-2, and severe-obese-LH: 3-6.

RESULTS

Higher LTL attrition was found in severe-obese than overweight individuals (p < 0.001). Multivariable model reveals that among severe-obese patients those with LH: 3-6 present higher LTL attrition than LH: 0-2 (p < 0.05). Univariate and multivariable models remarkably show that insulin resistance is higher both in overweight-LH: 3-6 vs overweight-LH: 0-2 (p < 0.001) and in severe-obese-LH: 3-6 vs severe-obese-LH: 0-2 (p < 0.0001), and HDL-C is lower in overweight-LH: 3-6 than overweight-LH: 0-2 (p < 0.05 and p < 001). Finally, most of the well-known (i.e., blood pressure, heart rate, waist to hip, triglycerides, and HDL-C) and novel CVD risk factors [i.e., inflammation markers (C-reactive protein, leukocytes, and chemoattractant protein-1), fibrinogen, and glucose homeostasis (i.e., insulin resistance, and glycated hemoglobin)] are substantially (p < 0.0001) altered in severe-obese-LH: 0-2 vs overweight-LH: 0-2, pointing to the fact that obesity leads to worsen the CVD/T2D risk factor profile.

CONCLUSION

Our study supports evidence that CYP27A1 genetic characterization identifies persons at higher risk to develop CVD and T2D, on which better converge preventive measures, and opens new perspectives on mechanisms that link obesity with aging-related disorders.

Pathophysiology of cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal-recessive lipid storage disease caused by mutations in the CYP27A1 gene, which lead to deficiency of the mitochondrial enzyme, sterol 27-hydroxylase, resulting in the accumulation of cholestanol in the serum and many affected lesions. To date, more than 50 different CYP27A1 mutations, including missense mutations, frameshifts, and splice site mutations, have been reported worldwide in patients with CTX. Clinical presentation is characterized by neonatal jaundice or cholestasis, refractory diarrhea, juvenile cataracts, tendon xanthomas, osteoporosis, coronary heart disease, and progressive neuropsychiatric disturbances; however, combinations of symptoms vary from patient to patient. Neuropsychiatric abnormalities include mental retardation or dementia, psychiatric symptoms, cerebellar signs, pyramidal signs, progressive myelopathy, peripheral neuropathy, extrapyramidal manifestations, and seizures. Replacement treatment with chenodeoxycholic acid in the early stage of the disease has been reported to improve or even prevent clinical symptoms of CTX. After significant neurological pathology is established, the effect of the treatment is limited and the deterioration of clinical manifestations may continue; therefore, early diagnosis of CTX is crucial.

Different phenotypes in identical twins with cerebrotendinous xanthomatosis: case series

Cerebrotendinous xanthomatosis (CTX) is a rare, genetically determined error of metabolism. The characteristic clinical symptoms are diarrhea, juvenile cataracts, tendon xanthomas and neuropsychiatric alterations. The aim of this study is to present a pair of identical adult twins with considerable differences in the severity of phenotype. With regards to neuropsychiatric symptoms, the predominant features were severe Parkinsonism and moderate cognitive dysfunctions in the more-affected individual, whereas these alterations in the less-affected patient were only very mild and mild, respectively. The characteristic increase in the concentrations of serum cholestanol and the lesion volumes in dentate nuclei in the brain assessed with magnetic resonance imaging were quite similar in both cases. The lifestyle conditions, including eating habits of the twin pair, were quite similar as well; therefore, currently unknown genetic modifiers or certain epigenetic factors may be responsible for the differences in severity of phenotype. This case series serves as the first description of an identical twin pair with CTX presenting heterogeneous clinical features.

Different phenotypes in identical twins with cerebrotendinous xanthomatosis: case series

Cerebrotendinous xanthomatosis (CTX) is a rare, genetically determined error of metabolism. The characteristic clinical symptoms are diarrhea, juvenile cataracts, tendon xanthomas and neuropsychiatric alterations. The aim of this study is to present a pair of identical adult twins with considerable differences in the severity of phenotype. With regards to neuropsychiatric symptoms, the predominant features were severe Parkinsonism and moderate cognitive dysfunctions in the more-affected individual, whereas these alterations in the less-affected patient were only very mild and mild, respectively. The characteristic increase in the concentrations of serum cholestanol and the lesion volumes in dentate nuclei in the brain assessed with magnetic resonance imaging were quite similar in both cases. The lifestyle conditions, including eating habits of the twin pair, were quite similar as well; therefore, currently unknown genetic modifiers or certain epigenetic factors may be responsible for the differences in severity of phenotype. This case series serves as the first description of an identical twin pair with CTX presenting heterogeneous clinical features.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

[Laboratory diagnosis of a rare congenital neurodegenerative disease: cerebrotendinous xanthomatosis]

Cerebrotendinous xanthomatosis is a rare neurodegenerative disease characterized by the accumulation of cholesterol and cholestanol in the brain and the tendons caused by mutations of the gene encoding sterol 27-hydroxylase (CYP27A1), which is involved in bile acid synthesis. The diagnosis is often missed and delayed because of the variable clinical presentation of the disease. Blood testing for cerebrotendinous xanthomatosis is routinely performed using gas chromatography-mass spectrometry measurement of elevated cholestanol level, and the diagnosis is confirmed by molecular genetic analysis. Early recognition and initiation of chenodeoxycholic acid therapy with hydoxymethyl‑glutaryl‑Coenzyme-A reductase inhibitors is critical to prevent irreversible neurological damage and permanent disability. The authors summarize the current knowledge about the pathomechanism, laboratory diagnosis and therapeutic options of cerebrotendinous xanthomatosis.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Psychiatric manifestations in cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare and severe, but treatable, inborn disorder of bile acid biosynthesis and sterol storage with autosomal recessive inheritance and variable clinical presentation. CTX treatment consists of chenodeoxycholic acid and must be started as early as possible to prevent permanent disability. Psychiatric manifestations are rare and non-specific, and often lead to significant diagnostic and treatment delay. Therefore, better recognition of the gamut of psychiatric manifestations in CTX can diminish the risk of misdiagnosis and irreversible neurological deterioration. We hereby describe the psychiatric features in CTX. A complete review of all published cases of CTX in the medical literature was undertaken and the case reports with psychiatric presentation were collected and analyzed. We also describe the psychiatric features in relation to the neurological semeiology in six patients with CTX diagnosed at the La Salpêtrière Hospital. We conclude that psychiatric manifestations in CTX follow a bimodal/bitemporal pattern, appearing early in the disease course in the form of a behavioral/personality disorder associated with learning difficulties or mental retardation, or manifesting in advanced disease in the setting of dementia as rich neuropsychiatric syndromes, such as frontal, orbitofrontal or frontotemporal syndromes of cortico-subcortical dementia encompassing behavioral/personality disturbance, affective/mood disorders or psychotic disorders. Behavioral/personality disturbance in childhood or adolescence, especially when accompanied by learning difficulties, should therefore lead to further investigation to exclude CTX, as early diagnosis and treatment is critical for prognosis.

Atypical parkinsonism and cerebrotendinous xanthomatosis: report of a family with corticobasal syndrome and a literature review

Cerebrotendinous xanthomatosis is an autosomal recessive inborn error of cholesterol metabolism. It presents with systemic and neurological symptoms, rarely including parkinsonism. Presented here are a clinical description of a new family with cerebrotendinous xanthomatosis and parkinsonism and a review of 13 additional cases reported in the literature. The index case developed corticobasal syndrome, previously not reported in cerebrotendinous xanthomatosis. His brother had parkinsonism with cerebellar features and cognitive impairment. In a literature review, median age of onset of parkinsonism was found to be 40 years. Nearly all patients had other neurological symptoms: cognitive (93%), pyramidal (93%), or cerebellar (53%). All patients had walking difficulties, with falls in 27%. Systemic features were common: cataracts (93%) or tendon xanthomata (87%). Frequent MRI abnormalities included cerebellar atrophy (100%), cerebral atrophy (80%), and dentate nuclei signal changes (80%). Functional dopaminergic imaging often demonstrated presynaptic denervation. Improvement with levodopa was frequent (91%) but mild. Progressive neurological decline occurred in 92% of patients despite treatment with chenodeoxycholic acid. Cerebrotendinous xanthomatosis should be considered in the differential diagnosis of atypical parkinsonism, including corticobasal syndrome, particularly with early age of onset and in the context of a complex neurological phenotype. Tendon xanthomata, early-onset cataracts, and radiological findings of cerebellar atrophy with lesions of the dentate nuclei are useful clinical clues. Symptomatic treatment with levodopa may help, but progressive neurological decline is frequent despite treatment with chenodeoxycholic acid.

Myoclonus and dystonia in cerebrotendinous xanthomatosis

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is an inherited neurometabolic disorder. The main neurological manifestations of the disease are pyramidal syndrome, ataxia, peripheral neuropathy, cognitive impairment, epilepsy, and psychiatric disturbances. Myoclonic dystonia has been reported on in the setting of various neurometabolic diseases. Anecdotal reports describe movement disorders associated with CTX, but no dystonia with myoclonic events.

METHODS

We collected clinical, biochemical, electrophysiological, neuroradiological, and genetic data of 6 patients with myoclonus and mild dystonia associated with CTX. From a systematic literature review, we analyzed 31 patients with movement disorders secondary to CTX.

RESULTS

Our 6 patients presented distal myoclonus with mild dystonia of the upper limbs. Myoclonus was of subcortical origin, based on neurophysiological recordings, and differed from oromandibular myoclonus previously described in CTX patients.

CONCLUSIONS

These results expand the phenotype of CTX and suggest that myoclonus and/or dystonia are underdiagnosed. In keeping with our findings, tremors previously observed in CTX patients might actually correspond to myoclonic events. We hypothesize that a dysfunction of the dentate nuclei-basal ganglia pathway may be involved.

Clinical relevance and neurophysiological correlates of spasticity in cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare neurometabolic disease due to defective activity of sterol 27-hydroxylase, with plasma and tissue cholestanol storage. Clinical phenotype is characterized by both systemic manifestations and neurological signs. Therapy with chenodeoxycholic acid (CDCA) suppresses abnormal bile acid synthesis. The purpose of the study was to assess the frequency and clinical relevance of spasticity in the CTX phenotype and to study the usefulness of transcranial magnetic stimulation (TMS) in detecting corticospinal tract damage and monitoring the effects of replacement therapy. Twenty-four CTX patients underwent clinical evaluation including general disability scores, pyramidal and cerebellar function scales, assessment of serum cholestanol and TMS. Nine patients who started CDCA therapy at baseline received clinical and neurophysiological follow up. All patients showed signs of pyramidal damage which were relevant for clinical disability in 18 out of 24 cases (75%), resulting in spastic paraparesis. TMS revealed corticospinal alterations even in subjects with mild clinical signs of corticospinal tract involvement. After CDCA treatment, serum cholestanol decreased to normal concentrations in all patients. Clinical picture was unchanged in seven out of nine cases; in two others pyramidal signs disappeared. A reduction in abnormal neurophysiological parameters was found. Spastic paraparesis is the most frequent and relevant neurological feature in CTX patients. Replacement treatment with CDCA can prevent the progression of pyramidal damage, especially if started early in the course of the disease. TMS represents a sensitive indicator of corticospinal tract dysfunction and subclinical improvements in pyramidal function after CDCA therapy.

Cerebrotendinous xanthomatosis patients with and without parkinsonism: clinical characteristics and neuroimaging findings

Parkinsonism in cerebrotendinous xanthomatosis (CTX) is rare. There are no published studies with imaging findings of dopamine transporter using (99m)Tc-[2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo [3,2,1] oct-2-yl] methyl] (2-mercaptoethyl) amino] ethyl] amino]-ethanethiolato(3-)-N2,N2,S2,S2]oxo-[1R-(exo-exo)] ((99m)Tc-TRODAT-1) SPECT in CTX patients. This report is on the clinical details of five genetically-proven CTX patients (two with and three without parkinsonism). Imaging findings using cranial magnetic resonance (MR) imaging and (99m)Tc-TRODAT-1 SPECT are also shown. Clinical correlation of neuroimaging findings and clinical presentations was made. A literature review of the clinical and neuroimaging features of eight CTX patients with parkinsonism reported in the English literature is also presented. The parkinsonian features of our two cases and the other eight reported cases occurred before the age of 50 years. The MR imaging study showed variable findings, in which, besides the common diffuse cerebral and cerebellar white matter lesions shown in CTX, several focal brain lesions were also noted. Of the focal lesions, substantia nigra abnormalities were seen only in the two cases with parkinsonism. The (99m)Tc-TRODAT-1 SPECT study showed different degrees of unilateral or bilateral abnormalities in the striatal binding in both visual and semiquantitative assessments. parkinsonism can be one of the neurologic presentations of CTX. Even though abnormal findings of the substantia nigra were detected in both of our CTX patients with parkinsonism, basal ganglion lesions have not been uniformly described in MR imaging findings of reported CTX patients with parkinsonism. (99m)Tc-TRODAT-1 SPECT study can be of value in the detection of striatal involvement, and the study results also suggest pre-synaptic dopamine neuron involvement in CTX patients with parkinsonism.

Juvenile parkinsonism: epidemiology, diagnosis and treatment

Juvenile parkinsonism, with onset prior to age 21 years, is a relatively rare syndrome. It is caused by a group of heterogeneous entities that can present with a clinical picture similar to idiopathic Parkinson's disease or manifest parkinsonism as part of a spectrum of other signs. Diagnostic testing is guided by the presenting symptoms and aimed at uncovering potentially reversible and/or treatable causes. If an underlying condition is found, treatment is tailored accordingly. Otherwise, treatment is symptomatic and relies on medications commonly employed to treat idiopathic Parkinson's disease. Juvenile parkinsonism patients tend to be plagued by treatment-induced complications, so caution must be employed.

Cerebrotendinous xanthomatosis: a critical update

Cerebrotendinous xanthomatosis (CTX) also known as van Bogaert–Scherer–Epstein syndrome, Thiebaut’s syndrome and cerebrotendinous cholesterosis, is an autosomal-recessive lipid-storage disease characterized by the triad of juvenile cataracts, tendon xanthomas and progressive neurodegeneration. Excess cholesterol and cholestanol are deposited in multiple organs, including the cerebrum, cerebellum, lens and tendons. Approximately 300 cases are reported worldwide, but it is suspected that the incidence of CTX is underestimated. The disease is attributed to approximately 50 mutations in the CYP27A1 gene coding for the enzyme sterol 27-hydoxylase, which is responsible for initial oxidation of the side chain of the cholesterol molecule in bile acid biosynthesis. CTX has varied clinical presentations, but no genotype–phenotype relationship has been documented. In some intrafamilial cases, clinical presentations may vary considerably. MRI for CTX is sensitive for diagnosis and classically demonstrates cerebral and cerebellar atrophy and xanthomatous lesions preferentially affecting the dentate nuclei. Patients have high serum levels of cholestanol with normal total cholesterol and increased urinary excretion of bile acids. Treatment of patients with chenodeoxycholic acid, particularly when used along with HMG-CoA reductase inhibitors (statins) or low-density lipoprotein apheresis, can normalize cholestanol levels as well as prevent further degeneration. Therefore, the need for early diagnosis is well documented in the literature, as it prevents the significant morbidity and mortality associated with this disease.

Movement disorders and inborn errors of metabolism in adults: a diagnostic approach

Inborn errors of metabolism (IEMs) may present in adolescence or adulthood with various movement disorders including parkinsonism, dystonia, chorea, tics or myoclonus. Main diseases causing movement disorders are metal-storage diseases, neurotransmitter synthesis defects, energy metabolism disorders and lysosomal storage diseases. IEMs should not be missed as many are treatable. Here we briefly review IEMs causing movement disorders in adolescence and adults and propose a simple diagnostic approach to guide metabolic investigations based on the clinical course of symptoms, the type of abnormal movements, and brain MRI abnormalities.

Cerebrotendinous xanthomatosis: case report with evidence of oxidative stress

Cerebrotendinous xanthomatosis is an autosomal recessive disorder of bile acid synthesis, characterized by mutation in the mitochondrial enzyme 27-hydroxylase that leads to an accumulation of cholestanol and cholesterol. Characterized clinically by premature bilateral cataracts, slowly progressive neurological deterioration with dementia, cerebellar and brainstem signs, peripheral neuropathy, and seizures, the disease presents pathologically with lipid granulomata with foamy histiocytes and cholesterol clefts. Replacement therapy with chenodeoxycholic acid slows progression of the disease but does not reverse neurological deficits. Here, we present the case of a 49-year-old woman diagnosed at autopsy with cerebrotendinous xanthomatosis, on the basis of bilateral Achilles tendon granulomas, and typical foamy histiocytic infiltration of the brain, most severe in the dentate nucleus, and a typical clinical presentation. To investigate the pathological manifestations of this disease further, we performed immunohistochemistry for N(epsilon)-(carboxymethyl)-lysine, an indicator of oxidative damage, and found strong labeling of cytoplasmic material within histiocytes. In summary, this case of undiagnosed cerebrotendinous xanthomatosis during life emphasizes the need for a greater awareness of the disease, and early diagnosis and treatment. Further, the involvement of oxidative stress in cerebrotendinous xanthomatosis indicates that combined therapy with chenodeoxycholic acid and antioxidants may improve clinical outcome.

Cerebrotendinous xanthomatosis: heterogeneity of clinical phenotype with evidence of previously undescribed ophthalmological findings

Cerebrontendinous xanthomatosis (CTX) is a rare autosomal recessive neurometabolic disease involving lipid metabolism. The classical phenotype is characterized by neurological dysfunction, tendon xanthomas and juvenile cataracts. Other ophthalmological findings have occasionally been reported. To gain more insight into the type and frequency of ophthalmological alterations in this multisystem metabolic disorder, we examined 13 CTX patients. Besides cataracts, found in all cases, the second most frequent ocular abnormality was paleness of the optic disk, which was found in 6 patients and was probably previously underestimated. Signs of premature retinal senescence were also observed. We discuss the possible relation between these ocular manifestations and the metabolic defect.