[Clinical and genetical features of Japanese early-onset facioscapulohumeral muscular dystrophy].

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant form of muscular dystrophy characterized by progressive weakness and wasting of the facial, shoulder-girdle and upper arm muscles. The gene locus for FSHD is mapped to the subtelomeric region of chromosome 4q35, in which smaller EcoRI fragments (10 to 33 kb) are detected in most families by Southern blot analysis. The purpose of this study is to clarify the frequency and clinical/genetical features of early-onset FSHD in Japanese patients with 4q35-FSHD. In a series of 231 patients from 145 families with 4q35-FSHD, there were 31 patients (13.4%; male: female = 12:19) of 29 families (20%) with early-onset FSHD, 16 of whom were sporadic. Genetic analysis revealed that they had significantly smaller sized EcoRI fragments (range, 10 to 23 kb; mean 14.1 kb) than the other patients (range, 12 to 33 kb; mean 19.6 kb) (p < 0.001, U-test). All patients with the smallest EcoRI fragments (10 to 11 kb) were sporadic cases with early onset. Mental retardation (10/11) and epilepsy (4/11) was often observed in them, but not in the other patients. In early-onset FSHD, tongue muscle involvement (8/31) and swallowing disturbance (2/31), which has been regarded as exclusion criteria of FSHD, were also present. The onset of gait disturbance was significantly earlier (mean age = 11.9) in early-onset FSHD compared to the other group (mean age = 28.7). All patients with early-onset FSHD showed gait disturbance before 28 years of age. In conclusion, Japanese early-onset FSHD patients tend to have large gene deletions on chromosome 4q35, and show severe and variable phenotypes.