Hypogammaglobulinemia in McArdle myopathy (glycogenosis type V).

Glycogenosis type V (McArdle) was the first myopathy to be enzymatically defined myopathy and has been found in approximately 120 patients. It is characterized by a myophosphorylase defect. In 2 patients with completely missing phosphorylase activity, muscle fiber necrosis and creatinine kinase elevation, we found reproducibly low gammaglobulins and low immunoglobulin-G. Compared with 124 nonmyopathic control patients with hypogammaglobulinemia, we did not find any established cause for low gammaglobulins in either case of McArdle disease. Myopathies with selected laboratory features or histopathology in common did not show changes in gammaglobulins or immunoglobulins. Unaffected family members had normal gamma-globulins and immunoglobulins. Therefore, gammaglobulins indicate an immunologic involvement in phosphorylase deficiency, and a potential for genomic co-localization.