Creatine kinase MB isozyme was found in the serum of 29 (91%) patients with progressive or congenital muscular dystrophy. The magnitude of its elevation exceeded that of other enzymes or isozymes studied. Mitochondrial aspartate aminotransferase (mAST) was detected in the serum of only seven patients (24%), all at an early stage of the disease, and it constituted without exception 5% or less of the total AST activity. Elevations of lactic acid dehydrogenase (LDH) activity were mainly due to increases of LDH 1-3 isozyme activity.
