This is one of many types of muscular dystrophy and has a much later age of onset than most. It is slowly progressive but the severity of disease varies widely. It also causes the most severe disease among facial and throat muscles with less involvement of limb musculature.
The first symptoms are noted around midlife, at an average age of 48 years. These consist of a combination of droopy eyelids and swallowing difficulties. Speech may also be slurred. Swallowing cold water and dry food takes longer than normal. Facial expressions are often limited and neck muscles may be weak. With time, weakness in the arms and legs is noted and, in more severe cases, there is evidence of muscle wasting in all areas. About 10% of patients are incapacitated by muscle weakness, especially in the legs, and may be confined to a wheelchair. The worsening of symptoms is slow and lifespan is usually normal.
This disorder is usually inherited as an autosomal dominant disease. The transmission pattern is vertical as affected parents pass on the mutation and disease directly to their children. Each child of an affected parent has a 50% chance of being similarly affected. New mutations are not common.
The diagnosis is most likely made by a neurologist or an ophthalmologist based on the specific pattern of muscle weakness. The symptoms worsen slowly with few patients becoming disabled. For those with severe eyelid drooping or swallowing difficulties, surgery is available. This lessens the severity of symptoms although there may be some recurrence after many years. Lifespan is normal.