Creatine Phosphokinase-Linked Immunoglobulin in a Patient with Hypokalemic Myopathy

Creatine Phosphokinase-Linked Immunoglobulin in a Patient with Hypokalemic Myopathy Dr. H. Arai, Department of Neurology, Motojima General Hospital, Ota, Gunma 373 (Japan) A macromolecular complex between creatine phosphokinase (CPK) and an immunoglobulin [1], termed macro-CPK type 1 [2, 3], is most likely an immune complex [4, 5] and has been identified in a variety of diseases including ischemic heart disease, neoplastic diseases and muscle disorders [5-7]. However, the biological and pathological significance of the complex is not fully understood. We report here the first observation of the presence of the macro-CPK type 1 in a patient with hypokalemic myopathy. A 49-year-old woman with no prior episode of muscle weakness was admitted because of increasing, symmetrical weakness in proximal upper and lower limbs over the previous month. She was unable to rise from a sitting position without using her arms. The affected muscle groups were hypotonic and tender without fasciculations. Laboratory data included: CPK 744 IU/1, aldolase 20.8 IU/1, lactate dehydrogenase 922 IU/1, serum Na 139mEq/l, serum K 2.0 mEq/1, serum CI 101 mEq/1. No autoantibodies were found. A CPK isozyme electophoresis demonstrated an extraband which was found to be migrating in a position between the CPK-MB and CPK-MM bands (fig. 1). The extra-CPK band constituted approximately 9% of the total CPK activity. A combination of thin layer gel filtration and im-munofixation electrophoresis revealed CPK-linked IgA (K and X). A morphological study of biopsied muscle demonstrated a selective atrophy of type 2B fibers in addition to a variation in size of muscle fibers and mild degenerative and regenerative changes without inflammatory cell infiltration. Immediately after admission. Intravenous supplementary therapy with potassium was started (fig. 2). A total of 420 mEq of potassium chloride was given during the first