Neurological symptoms, genotype-phenotype correlations and ethnic-specific differences in Bulgarian patients with Wilson disease.

OBJECTIVES: The aim of our study was to characterize the neurological symptoms in Bulgarian patients with Wilson disease (WD), to investigate genotype-phenotype correlations, and to test whether there are differences in phenotype between patients of different ethnic origin. PATIENTS AND METHODS: A total of 126 Bulgarian patients with WD were included in the study. Detailed history, physical and neurological examination, laboratory investigation of copper metabolism, slit-lamp examination, abdominal ultrasound, magnetic resonance imaging/computed tomography of the brain, molecular genetic testing, and statistical analysis were performed. RESULTS: Eighty-two patients demonstrated neurological signs. Tremor and dysarthria were most frequently observed. Rigidity, bradykinesia, and pyramidal signs were found in >25% of the patients. Dystonia, chorea, athetosis, ballismus, and epilepsy were rarely observed. We identified a total of 27 mutations of ATP7B. The most frequent mutation is p.H1069Q found on at least 1 allele in 78% of the patients. We did not find a significant correlation between p.H1069Q homozygosity and age of onset, ceruloplasmin level, and urinary copper excretion. The patients homozygous for p.H1069Q presented more frequently with hepatic signs. Mutations predicted to cause production of truncated protein are associated with earlier age at onset and lower ceruloplasmin level. In contrast to Bulgarian patients, Roma patients had an earlier disease onset and more frequent hepatic manifestation. CONCLUSIONS: WD presents with a variety of neurological signs. The mutation p.H1069Q is not uniformly associated with late onset and neurological presentation. Frameshift and nonsense mutations lead to severe phenotype. There are ethnic-specific differences in disease manifestation.

Highly variable neural involvement in sphingomyelinase-deficient Niemann-Pick disease caused by an ancestral Gypsy mutation.

Niemann-Pick disease (NPD), an autosomal recessive disorder resulting from mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene, is subdivided into the acute, lethal neuronopathic type A, and the chronic visceral type B, explained by the different residual activity levels of acid sphingomyelinase (ASMase). An increasing number of reports on intermediate forms, challenging this traditional clinical classification, have described a broad range of neurological manifestations; however genotype-phenotype correlations have been compromised by relatively small sample sizes and/or allelic heterogeneity. Here we present a genetically homogeneous group of 20 Gypsy patients with intermediate NPD, where we observed a surprising diversity of neurological features. All affected subjects were homozygous for the same ancestral mutation, W391G in SMPD1, yet displayed the entire spectrum of phenotypic variation observed previously in unrelated affected subjects of diverse ethnicity and disease-causing mutations, ranging from subclinical retinal involvement to severe ataxia, cognitive deficits and psychiatric disorders. The clinical heterogeneity of W391G homozygotes points to additional factors, beyond SMPD1 and residual ASMase, which determine the localization, extent and severity of neural involvement. The phenotype similarity of affected relatives suggests a possible role of genetic modifying factors. In practical terms, W391 is common in the Gypsy population and the diagnosis of NPD should be borne in mind despite the atypical course of the disease. Generally, our findings indicate that mutation analysis is of limited value in predicting brain damage, and the option of enzyme replacement therapy should be considered in intermediate NPD.