Myalgic phenotype and preserved muscle strength in adult-onset acid maltase deficiency.

Adult-onset acid maltase deficiency is a rare disorder characterized by progressive proximal muscle weakness and early respiratory insufficiency. We present a case of a 53-year-old woman who presented with several years of severe, diffuse myalgia and no evidence of weakness on examination. Further testing revealed a mildly elevated serum creatine kinase, a subtle vacuolar myopathy, decreased skeletal muscle α-glucosidase activity, and causative mutations in the responsible GAA gene. While likely very uncommon, adult-onset acid maltase deficiency may present with diffuse strength-sparing myalgia.