However, the lack of a precise genotype–phenotype correlation in many cases requires a more comprehensive genetic analysis of both D4Z4 alleles and SMCHD1. In this work, we report the sequence analysis of SMCHD1 in a cohort of clinically defined FSHD patients in order to assess the distribution of SMCHD1 variants, considering the D4Z4 size (short fragment: 1-7RU, borderline fragment: 8-10RU and normal fragment: >11RU). This evidence concerns the gene SMCHD1 and facioscapulohumeral muscular dystrophy.