Phenotypic and genotypic heterogeneity of dominantly inherited amyotrophic lateral sclerosis.

Twenty-seven cases of hereditary amyotrophic lateral sclerosis (ALS), belonging to 8 families, are reported. The analysis of the pedigrees suggests an autosomal dominant transmission, apparently with incomplete penetration. The mean age at onset of symptoms was 50.3 (SD 12.4) years. The mean duration of the disease was 31.2 (SD 20.4) months, ranging from 9 to 86. The median survival time was 24 months. The degree of variation of some quantitative characters, both within and among families, was statistically analyzed. The results support the hypothesis of a phenotypic and genetic heterogeneity of autosomal dominant transmitted ALS.