[A family with facioscapulohumeral muscular dystrophy and hereditary long QT syndrome].

We describe a family with facioscapulohumeral muscular dystrophy (FSHD) and hereditary long QT syndrome (LQT) for three generations. The proband, a 50-year-old woman, had noticed difficulty in raising the upper extremities since the age of 40. At the age of 48, she was admitted to our hospital because of arrhythmia attack. She, her mother, and one of her three children were diagnosed as having LQT. These three individuals and the proband's two siblings were clinically diagnosed as having FSHD which was confirmed by genetic analysis using EcoR1. FSHD is an autosomal dominant disorder and the gene locus is mapped to chromosome 4q35-ter, but the gene has not been isolated. LQT is a group of disorders which cause syncope and sudden death from ventricular arrhythmia in an autosomal dominant fashion. Four loci for this syndrome (LQT1-4) have been known, and three of the genes have been shown to encode ion-channels. Genetic analysis of the proband failed to detect any of previously known mutations in the LQT1, LQT2, and LQT3 genes. The locus for LQT4 has been mapped to chromosome 4q25-7. There have so far been no report of FSHD associated with LQT. Although the pathogenesis is unclear, we speculate that these two diseases are linked each other on chromosome 4q.