RESUMEN
BACKGROUND: Between January 1993 and December 2003, 19 patients with familial prion diseases due to the D178N mutation were referred to the regional epidemiological registry for spongiform encephalopathies in the Basque Country in Spain, a small community of some 2,100,000 inhabitants. METHODS: Ten further patients belonging to the same pedigrees were retrospectively ascertained through neurological or neuropathological records. In four of the patients, the diagnosis was confirmed by analysing DNA obtained from paraffin blocks. In this article, we report on the clinical, genetic, and pathological features of the 23 patients carrying the D178N mutation confirmed by genetic molecular analysis. Haplotyping studies suggest a founder effect among Basque born families, explaining in part this unusually high incidence of the D178N mutation in a small community. Only two patients (8%) lack familial antecedents. RESULTS: We have observed a phenotypic variability even among homozygous 129MM patients. Our findings challenge the currently accepted belief that MM homozygosity in codon 129 is always related to a fatal familial insomnia (FFI) phenotype. Indeed, seven out of 17 patients with a 129MM genotype in this series presented with a Creutzfeldt-Jakob disease (CJD) clinicopathological picture. CONCLUSIONS: The considerable clinical and pathological overlapping observed among homozygous 129MM patients favours the view that FFI and CJD178 are the extremes of a spectrum rather than two discrete and separate entities. Other genetic or environmental factors apart from the polymorphism in codon 129 may play a role in determining the phenotypic expression of the D178N mutation in the PRNP gene.
Asunto(s)
Amiloide/genética , Síndrome de Creutzfeldt-Jakob/genética , Variación Genética/genética , Fenotipo , Mutación Puntual/genética , Adulto , Edad de Inicio , Anciano , Codón , Síndrome de Creutzfeldt-Jakob/etnología , Análisis Mutacional de ADN , Femenino , Efecto Fundador , Haplotipos , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Proteínas PrPSc/genética , Estudios Prospectivos , Trastornos del Inicio y del Mantenimiento del Sueño/epidemiología , EspañaRESUMEN
BACKGROUND: Frontotemporal dementia with parkinsonism is often linked to chromosome 17 and is related to mutations in the MAPT gene. In some families the genetic basis is still unknown. The authors report two pedigrees with FTDP-17 harboring a novel mutation (K317M) in exon 11 in the MAPT gene. METHODS: The authors identified two apparently unrelated pedigrees with an autosomal dominant neurodegenerative condition. Thirteen patients were examined and eight autopsies were performed. RESULTS: Mean age at onset was 48 years. Mean disease duration was 6 years. Dysarthria often heralded the disease. All cases had parkinsonism and pyramidalism and half of them had amyotrophy. Behavioral or personality changes were not a prominent feature. Cognitive decline appeared late in the evolution. Neuropathologically, a massive degeneration of the substantia nigra without Lewy bodies was a constant finding. A variable degree of frontotemporal atrophy was found. Corticospinal tract degeneration and anterior horn neuron loss were present in six of seven autopsies in which the spinal cord was examined. An extensive deposition of abnormal tau protein in a mixed pattern (neuronal, glial) was observed. Pick's bodies were not seen. Biochemical analysis of tau revealed two bands of 64 and 68 kDa. CONCLUSION: Genetic analysis revealed the same novel mutation (K317M) in exon 11 of the MAPT gene in both pedigrees. A common haplotype between members of the two pedigrees suggests that they belong to the same family.
