Clinical and genetic characteristics based on the Japanese patient registry for facioscapulohumeral muscular dystrophy: a nationwide analysis.

The Japanese patient registry for facioscapulohumeral muscular dystrophy (FSHD) was launched in September 2020, enrolling patients genetically confirmed to have FSHD. This study aimed to analyze clinical and genetic characteristics based on data from the Japanese FSHD registry. Core items were collected from the TREAT-NMD FSHD dataset, version 1.0. By the end of June 2024, over 200 patients were enrolled, with 161 successfully registered after confirmation. Among them, 156 had FSHD1 and 5 had FSHD2; 81 had affected family members; 116 were ambulatory; 73 had respiratory dysfunction; 22 required mechanical ventilation; 8 had cardiac dysfunction; 4 had retinopathy; and 22 had hearing loss. In patients with FSHD1, the median number of D4Z4 repeats was four, with a low proportion of long repeats. D4Z4 repeat counts influenced age at disease onset, site-specific muscle weakness onset, respiratory function, retinopathy, and hearing loss. Notably, female patients were more likely to have early facial weakness and hearing loss. Our data suggest population diversity in D4Z4 repeat numbers and sex differences. We aim to collaborate with patient groups to enroll more participants and gather more accurate epidemiological data, including cases of FSHD2. Additionally, we plan to investigate racial differences through international collaboration.