Activity, creatine kinase, and myoglobin in Duchenne muscular dystrophy: a clue to etiology?

Large and seemingly random fluctuations in the serum levels of creatine kinase (CK) and myoglobin (Mb) have been noted in patients with Duchenne muscular dystrophy. We studied seven affected boys, aged 2 to 9 years. Blood was drawn for CK and Mb every 4 hours, and the boys' activity was documented hourly for 4 days. There was a close correlation between serum levels of CK and Mb with physical activity. Fluctuations in serum levels of CK and Mb are not random and may result from an abnormality of fatty acid metabolism.