Geographic distribution of 18 autosomal recessive disorders in the French Canadian population of Saguenay-Lac-Saint-Jean, Quebec.

We analysed the geographic distribution of 770 patients and 1084 obligate carriers of 18 autosomal recessive disorders that have a high incidence in Saguenay-Lac-Saint-Jean (SLSJ) (Quebec). The places of birth of the patients and the obligate carriers were found to be unevenly distributed in SLSJ. A statistically significant higher number of places of birth than expected (p < or = 0.05) was observed in Saguenay and Lac-Saint-Jean (LSJ) East, where the immigration was mainly the fact of individuals coming from Charlevoix. A significantly lower number of places of birth than expected was found in LSJ West, and in some municipalities in which the immigration and the contribution of the ancestors from Charlevoix was low. The geographic distribution of inbreeding and kinship only partially explained the geographic distribution of the disorders. The individuals who had both parents and all four grandparents born in SLSJ were at a higher risk of having a recessive disorder. While the genes of these disorders are still being introduced in SLSJ, they are also being dispersed in other regions and outside Quebec by emigrants from SLSJ.