[Chronic proximal spinal amyotrophies in Tunisia. Clinical, genetic, epidemiologic and histopathologic study].

The results of a clinical, pathological, genetic and epidemiological study of 101 cases of chronic proximal spinal muscular atrophy are reported. Ages at onset allow to distinguish clearly an infantile, a juvenile and an adult groups. The infantile and juvenile groups comprising 93 p. 100 of the patients, were characterized by onset before the age of 20 (54 p. 100 before age 5) and by a large intra- and interfamilial clinical variability. The severity of the disease was unrelated either to sex or the sporadic or familial nature of the disease. On the other hand it was closely related to age at onset and to the pathology of the muscles. There seems to be no genetic heterogeneity in this group. Inheritance is of the autosomal recessive type in the great majority of cases. Certain sporadic cases may be due to a dominant mutation or to a phenocopy, as suggested by segregation analysis. The adult group, comprising 6 patients, included 4 cases of autosomal dominant inheritance without consanguinity of the parents, and one case of dominant inheritance.