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|Facioscapulohumeral Muscular Dystrophy|
Facioscapulohumeral muscular dystrophy (FSHD) is the third most common hereditary disease of muscle after Duchenne and myotonic dystrophy. It initially affects muscles of the face (facio), shoulders (scapulo), and upper arms (humera) with progressive weakness. Life expectancy is normal, but some individuals become severely disabled.
Disease progression is typically very slow, with intermittent spurts of rapid muscle deterioration. Onset is usually in the teenage years but may occur as late as age 40. Muscles around the eyes and mouth are often affected first, followed by weakness around the lower shoulders and chest. A particular pattern of muscle wasting causes the shoulders to appear to be slanted and the shoulder blades to appear winged. Muscles in the lower extremities may also become weakened. Reflexes are impaired only at the biceps and triceps. Changes in facial appearance may include the development of a crooked smile, a pouting look, flattened facial features, or a mask-like appearance. Some patients cannot pucker their lips or whistle and may have difficulty swallowing, chewing, or speaking.
Other symptoms may include hearing loss (particularly at high frequencies) and lordosis, an abnormal swayback curve in the spine. Contractures are rare. Some FSHD patients feel severe pain in the affected limb. Cardiac muscles are not affected, and the pelvic girdle is rarely significantly involved. An infant-onset form of FSHD can also cause retinal disease and some hearing loss.
Facioscapulohumeral muscular dystrophy is associated with mutations in the FSHMD1A gene. It is inherited in an autosomal dominant pattern.