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1/3. Rhythmic cortical myoclonus in Niemann-Pick disease type C.

    We here describe a patient with late-infantile Niemann-Pick disease type C (NPC) presenting with worsening myoclonus, seizures, cerebellar symptoms, mild mental impairment, and gaze palsy. Electroencephalographic (EEG) -polymyographic examinations showed abnormally high and diffuse background alpha-activity, enhanced by intermittent photic stimulation. The electromyographic (EMG) showed quasirhythmic myoclonic jerks during motor activation. EEG-EMG frequency analysis (better than jerk-locked back-averaging) demonstrated the cortical origin of the myoclonus. Our observations indicate that cortical myoclonus may occur as the main symptom of NPC. ( info)

2/3. Subclinical course of adult visceral Niemann-Pick type C1 disease. A rare or underdiagnosed disorder?

    We present the third case of Niemann-Pick disease type C without neurological symptoms. The patient was a 53-year-old woman without significant prior health problems who died of acute pulmonary embolism. autopsy findings of hepatosplenomegaly, lymphadenopathy and ceroid-rich foam cells raised the suspicion of the visceral form of acid sphingomyelinase deficiency (Niemann-Pick disease type B; NPB) or a much rarer disorder, variant adult visceral form of Niemann-Pick disease type C (NPC). To verify the histopathological findings, SMPD1, NPC1 and NPC2 genes were analysed. Two novel sequence variants, c.1997G>A (S666N) and c.2882A>G (N961S) were detected in the NPC1 gene. No pathogenic sequence variants were found either in the SMPD1 gene mutated in NPB or in NPC2 gene. The pathogenicity of both NPC1 variants was supported by their location in regions important for the protein function. Both variations were not found in more than 300 control alleles. Identified sequence variations confirm the diagnosis of the extremely rare adult visceral form of Niemann-Pick disease type C, which is otherwise dominated by neurovisceral symptoms. Although only three patients have been reported, this (most probably underdiagnosed) form of NPC should be considered in differential diagnosis of isolated hepatosplenomegaly with foam cells in adulthood. ( info)

3/3. The adult form of Niemann-Pick disease type C.

    Niemann-Pick disease type C (NPC) is a fatal neurovisceral lipid storage disease of autosomal inheritance resulting from mutations in either the NPC1 (95% of families) or NPC2 gene. The encoded proteins appear to be involved in lysosomal/late endosomal transport of cholesterol, glycolipids and other molecules but their exact function is still unknown. The clinical spectrum of the disease ranges from a neonatal rapidly fatal disorder to an adult-onset chronic neurodegenerative disease. Based upon a comprehensive study of 13 unrelated adult patients diagnosed in france over the past 20 years as well as the analysis of the 55 other cases published since 1969, we have attempted to delineate the major clinical, radiological, biochemical and genotypic characteristics of adult NPC. overall, mean age at onset ( /-SD) of neuropsychiatric symptoms was 25 /- 9.7 years. The diagnosis of NPC was established after a mean delay of 6.2 /- 6.4 years and the mean age at death (calculated from 20 cases) was 38 /- 10.2 years. Major clinical features included cerebellar ataxia (76%), vertical supranuclear ophthalmoplegia (VSO, 75%), dysarthria, (63%), cognitive troubles (61%), movement disorders (58%), splenomegaly (54%), psychiatric disorders (45%) and dysphagia (37%). Less frequent signs were epilepsy and cataplexy. During the course of the disease, clinical features could be subdivided into (i) visceral signs (hepatomegaly or splenomegaly), (ii) cortical signs (psychiatric cognitive disorders and epilepsy); and (iii) deep brain signs (VSO, ataxia, movement disorders, dysarthria, dysphagia, cataplexy) which exhibited different evolution patterns. Asymptomatic and non-evolutive visceral signs were often noticed since early childhood (38.5% of our patients), followed by mild cortical signs in childhood (learning difficulties) and early adulthood (62% of cases among which 38% were psychiatric disorders). Deep brain signs were observed in 96% of patients and were usually responsible for death. In general, there was a good correlation between clinical signs and the localization of brain atrophy on MRI. The 'variant' biochemical phenotype characterized by mild abnormalities of the cellular trafficking of endocytosed cholesterol was over-represented in the adult form of NPC and seemed associated with less frequent splenomegaly in childhood and lesser psychiatric signs. Involvement of the NPC1 gene was shown in 33 families and of the NPC2 gene in one. Improving the knowledge of the disease among psychiatrists and neurologists appears essential since emerging treatments should be more efficient at the visceral or cognitive/psychiatric stages of the disease, before the occurrence of widespread deep brain neurological lesions. ( info)

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