Onset

There is wide variability in age of onset with FSHD. Symptoms typically begin to appear in the teen years. In some cases, individuals do not begin to experience the muscle weakness characteristic of FSHD until well into adulthood. A very rare form of FSHD, often called infantile FSHD or IFSHD, is particularly debilitating, with symptoms beginning in infancy or early childhood.

Cause

FSHD is caused by aberrant expression of a gene called DUX4. In a healthy individual, DUX4 is active for only a short time in early embryonic development. In individuals with FSHD, the DUX4 gene remains “on” long after it is supposed to be silenced. This activation leads to surplus production of the DUX4 protein, which causes the gradual destruction of muscle cells throughout the body.

Symptoms

People living with FSHD experience a broad range of symptoms, including:

• Facial muscle weakness, which can make it difficult to smile or use a straw
• Weakness in all major muscle groups, including arms, torso, legs and abdomen
• Joint and spinal abnormalities, including protrusion of the shoulder blades
• Limited mobility

Treatment

There are currently no approved disease-modifying treatments for FSHD.