<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by facioscapulohumeral muscular dystrophy ? [/INST] Facioscapulohumeral muscular dystrophy has an estimated prevalence of 1 in 20,000 people. About 95 percent of all cases are FSHD1; the remaining 5 percent are FSHD2. </s>