This laboratory has defined several mutations in muscle diseases which mimic idiopathic inflammatory myopathy, (IIM, polymyositis or dermatomyositis), in particular, phosphofructokinase (PFK) deficiency (Type VII glycogenosis) and acid maltase (GAA) deficiency (Type II glycogenosis). Some patients with each of these autosomal recessive diseases have been shown to be genetic compounds, with different mutations on the alleles from each parent. In this protocol, we seek permission to receive and perform genetic screening on samples of tissue, blood, or DNA from patients with known metabolic muscle diseases, their family members, patients with undiagnosed muscle diseases, and groups of control subjects. Although we will know the names and histories of the patients, and may choose to admit them under other protocols for further studies, the tests we propose to perform on their DNA are currently only of laboratory interest and we believe that the outcome has no implications for the clinical care of the subjects. We propose to obtain oral consent, as appropriate to take a limited history and to speak to the patient's physician, from those patients and family members we speak to directly. All specimens obtained in family studies of a particular disease (e.g., PFK deficiency or GAA deficiency) will be obtained after written consent and will be tested only for the genes of the particular disease under study. After completion of those tests, the DNA, or products derived from it will be stored only under code so that it may be used as a control sample for other studies.