[Clinical study of familial forms of amyotrophic lateral sclerosis. Review of the literature].

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder involving both upper and lower motor neurons. The disease is possibly due to several factors, including a genetic one. This is supported by the existence of 5 to 10 p. 100 familial cases. In these pedigrees, the transmission is autosomal dominant, with a high penetrance (> 90 p. 100). We studied the phenotypes of these familial cases, in reviewing the literature on familial ALS (FALS). It has been noted that FALS are heterogeneous, with different age of onset, site of onset and disease duration. Moreover, in FALS, onset is earlier than in the sporadic form (48 vs 60 years, as usually reported in the literature). We also frequently noted sensory disorders (20 p. 100), onset on the lower limbs (46 p. 100) and decreased or absent ankle-jerks (75 p. 100) in FALS patients.