A Chinese-American family with a severe X-linked congenital autophagic vacuolar myopathy (AVM) affecting 7 boys is reported from the National Center of Neurology and Psychiatry, Kodaira, Tokyo, and Utano National Hospital, Kyoto, Japan; and Shandong University, Jinan, China. One of the 7, a 7-year-old, was born with hypotonia and hypoventilation requiring respiratory support for 3 days. Nasogastric tube feeding was necessary until age 2 and ½ years. Motor milestones were delayed, sitting at 9 months and walking with support at 2 years. Subsequently, motor development deteriorated, with progressive muscle weakness and crawling at age 7. Serum CK was elevated at 1.962 IU/L. Examination showed generalized muscle atrophy and weakness, including facial and neck muscles. Mentation was normal. EKG showed incomplete right bundle-branch block, and echocardiography revealed left ventricular hypertrophy. EMG of the right biceps brachii showed complex repetitive discharges without fibrillation potentials or positive sharp waves and low-amplitude, short-duration motor unit potentials, compatible with a chronic myopathy. Muscle pathology showed autophagic vacuoles with sarcolemmal features of X-linked myopathy with excessive autophagy (XMEA), suggesting allelism to XMEA, with a more severe clinical presentation.