Incidence of FSHD

The most common form of FSHD by far is FSHD type 1A (chromosome 4-linked FSHD). A conservative estimate of incidence is 1 in 14,000 births throughout the world; however, due to increased experience with FSHD, population-based research and improved genetic testing, this estimate may be low; actual incidence may be 1 in 7,500.

FSHD type 1B (non-chromosome 4-linked FSHD) is much rarer than FSHD type 1A (chromosome 4-linked FSHD). There is no generally accepted estimate of its incidence, but incidence is unlikely to exceed 2% of all cases of FSHD.

Infantile FSHD (IFSHD) is characterized by onset in early childhood. There is no generally accepted estimate of its incidence, but it is rare.