AMD is a glycogen storage disease that affects all age groups. In both childhood and adult forms, the classic clinical picture is that of a progressive myopathy that may resemble polymyositis or limb girdle muscular dystrophy. Respiratory muscle involvement is common, may occur early in the course of the disease, and is the most frequent cause of mortality from AMD. These findings underscore the need to consider AMD in the differential diagnosis of unexplained respiratory insufficiency. We have described the case of one patient in whom respiratory failure was the initial symptom and two other cases in which the patient had progressive muscular weakness and subsequent respiratory failure. A review of the literature revealed that respiratory muscle weakness has been reported in 21 of 43 cases of AMD in adults. In 10 cases respiratory insufficiency was preceded by only mild or moderate weakness.