Progression of FSH is slow. There are long periods of stability interspersed with shorter periods of rapid muscle deterioration and increased weakness. Nearly half of those with FSH retain the ability to walk throughout their lives. Fukuyama congenital muscular dystrophy is one form that has been clearly described. It involves severe weakness of the facial and limb muscles with a generalized lack of muscle tone usually appearing before nine months.
Joint contractures are common.
Brain abnormalities are present, speech problems, and often, seizures are associated with the disease. Another form of CMD appears to be related to a deficiency or break down of the protein merosin, which ordinarily lies outside muscle cells and links them to the surrounding tissues. The disease is similar to Fukuyama dystrophy, with muscle weakness seen during infancy, severe and early contractures, and often, joint deformities. It has been named congenital muscular dystrophy with merosin deficiency. Signs of eye and facial weakness, as well as difficulty in swallowing follow this.