MYH6 and facioscapulohumeral muscular dystrophy: For FSHD, 76.5% (26/34) of muscle biopsies from quadriceps (Fig. 4A–E) and 90.9% (10/11) from tibialis anterior (Fig. 4F) contained one or more muscle fibres containing Dev MyHC, indicating active muscle regeneration (Tables 1 and 2).