Genetic epidemiology of sensorimotor polyneuropathy with or without agenesis of the corpus callosum in northeastern Quebec.

Sensorimotor polyneuropathy with or without agenesis of the corpus callosum (McKusick number 218000) is a disorder that has a high frequency in Saguenay-Lac-St-Jean (SLSJ), a geographically isolated region of north-eastern Quebec. The incidence at birth and the carrier rate were estimated, respectively, at 1/2117 liveborns and 1/23 inhabitants. Remote consanguinity was found in several polyneuropathic families while the mean kinship coefficient was 2.7 times higher in the polyneuropathic group than in control groups. The birth places of the individuals with sensorimotor polyneuropathy and their parents did not show a clustered nonuniform distribution. The genealogical reconstruction suggests that the high incidence of polyneuropathy in SLSJ is likely to be the result of a founder effect. It also suggests that a unique mutation accounts for most, if not all, of the cases of sensorimotor polyneuropathy known in this region.