[Familial hemiplegic migraine. Localization of a responsible gene on chromosome 19].

Familial hemiplegic migraine is an autosomal dominant disorder of unknown pathogenesis in which the migrainous attacks are marked by the occurrence of a transient hemiplegia during the aura. The aim of our study was the identification of the affected gene. The first step was the chromosomal mapping of the affected gene, for which we used a "candidate gene" strategy. The first candidate gene was the gene responsible for CADASIL. While investigating CADASIL, mapped previously to chromosome 19, we observed that some patients had recurrent attacks of migraine with aura. Although the clinical and neuroimaging features of familial hemiplegic migraine differ markedly from CADASIL, we hypothesized that the same gene could be involved in the pathogenesis of both conditions. We chose two large pedigrees for linkage analysis of familial hemiplegic migraine. A maximum lodsore > 8 was found with two markers that are strongly linked to CADASIL. Multilocus linkage analysis located the affected gene within an interval of about 30 cM on chromosome 19, containing the gene responsible for CADASIL. At this step it's not possible to conclude that CADASIL and familial hemiplegic migraine are due to the same mutated gene. It will be necessary to analyse other familial hemiplegic migraine and CADASIL families in order to reduce the size of their respective interval and ultimately identify the mutated gene(s).