[Genetic study of spinocerebellar hereditary degenerations in Tunisia. Role of consanguinity in their occurrence].

The genetic analysis of 101 genealogical trees of families with spinocerebellar heredo-degeneration enabled the authors to specify the transmission inheritance for each clinical type. Autosomic recessive transmission has been observed for Friedreich's ataxia (68 out of 69 families), Pierre-Marie's heredo-ataxia (15 families) and familial spastic paraplegia (2 families). A dominant mode of transmission has been observed in 13 families affected by familial spastic paraplegia (Strumpell-Lorrain) and in only one family with Friedreich's ataxia (an intermediate or incomplete form). It has also been observed that the consanguinity rate among this group of families is very high compared with that of the general tunisian population (25%). Marriage between cousins occurs in 75% of the cases of Friedreich's ataxia, in 78% of the cases of Pierre-Marie's heredo-ataxia and in only 61% of familial spastic paraplegia of Strumpell-Lorrain. The authors have come to the conclusion that the recessive autosomic transmission of the spino-cerebellar heredo-degenerative diseases are closely related to a high consanguinity rate.