Biopsy-proven alpha-glucosidase deficiency with normal lymphocyte enzyme activity

Alpha‐glucosidase deficiency is a rare cause of muscle disease in adults. The diagnosis relies on recognition of the salient clinical features and determination of significantly reduced alpha‐glucosidase (GAA) activity. Lymphocytes are the usual tissue for diagnostic enzymology; discrepant results from analyses of different tissues are unusual. We report a patient with clinical, electromyographic, and biopsy findings indicative of alpha‐glucosidase deficiency whose muscle and lymphocyte enzyme results were markedly discrepant on multiple analyses. As a result, we conclude that all patients with suspected alpha‐glucosidase deficiency and a normal lymphocyte GAA assay should also have a determination of GAA activity in muscle or skin fibroblasts. Muscle Nerve 29: 440–442, 2004