Familial dyskinesia and facial myokymia (FDFM): Follow-up of a large family and linkage to chromosome 3p21-3q21.

We previously reported a five-generation family manifesting an autosomal dominant disorder of facial myokymia and dystonic/choreic movements (FDFM). The dyskinetic episodes are initially paroxysmal but may become constant. With increasing age they may lessen or even disappear. The previous study excluded nine candidate genes chosen for their association with myokymia or chorea and two regions containing single or clustered ion channel genes. We now report identification by whole genome linkage analysis of a broad region on chromosome 3p21-3q21 that segregates with the disease in all 10 affected members in three generations who participated in the study. GENEHUNTER-MODSCORE Version 2.0.1 provided a maximum multipoint LOD score of 3.099. No other disorders primarily characterized by myokymia, dystonia, or chorea are known to map to this region. Identification of additional families with FDFM may narrow the critical region and facilitate the choice of candidate genes for further analysis.