The gene encoding dystrophin, a protein essential to proper functioning of the cytoskeletal system, appears to be damaged by a frameshift mutation. This mutation occurs early on in the gene, resulting in complete loss of dystrophin. As a result, signs of this condition usually appear in early childhood, when the child has difficulty walking or lifting oneself up. The legs and arms of the individual are affected. In addition, the muscles of the diaphragm weaken.
Breathing becomes difficult, and pulmonary infections are a constant risk.
By the early teens, an affected individual may rely completely on a wheelchair, and possibly an assisted breathing device. In some instances, intellectual ability is adversely affected. The individual usually dies in the twenties. FSHD is usually less severe than Duchenne muscular dystrophy. However, it remains a very debilitating disorder, and for this reason, much research is being done.