[Adult form of acid maltase deficiency presenting with pattern of muscle weakness resembling facioscapulohumeral dystrophy].

We report a 61-year-old female patient with adult form of acid maltase deficiency showing many clinical similarities to facioscapulohumeral muscular dystrophy (FSHD). She developed difficulty in raising her right arm in her thirties followed by leg weakness. She had the typical features of FSHD, including bilateral scapular winging sparing the levator scapulae and deltoid muscles, and Beevor's sign. Muscle involvement was asymmetrical. Facial muscles were not affected, while the neck flexor was weak. No muscle shortening or joint contracture was observed. On muscle CT, the lumbar paravertebral, gluteal and thigh muscles were replaced by adipose tissue, while the rectus femoris, gracilis, and sartorius muscles were spared. Serum creatine kinase level was not elevated. Muscle biopsy showed some vacuoles and many granular inclusions with high acid phosphatase activity. Acid maltase activity was very low in both muscle and cultured skin fibroblasts. Absence of shortening of affected muscles appears to be the characteristic finding suggesting metabolic myopathies with minimal fibrosis, rather than FSHD.