A motorcycle accident five years ago that damaged his cervical spinal cord left a 65-year-old African-American man with left spastic hemiparesis (almost hemiparalysis). He takes baclofen for the spastic pain in his left extremities. The man is 6 ft tall and weighs 200 lb (up from 160 lb since the accident). For the past five years, he has taken glyburide for diabetes mellitus. Eczema on his face and both hands is controlled with occasional use of topical steroid cream. During the past three years, the patient’s creatine kinase (CK) has ranged from 1,000 to 2,000 units/L. His CK-MB and his CK-MM are consistently 10%-20% and 80%-90%, respectively. ECGs have always been normal; he has never had symptoms of cardiac ischemia. Muscle biopsy of the right deltoid was nonspecific. What is causing his elevated CK? And how should I proceed now?
—Oh J. Lee, MD, Munster, Ind.

Clinical evidence of myopathy or connective tissue disease, such as weakness, fatigue, or muscle cramping, on the side unaffected by the spinal-cord injury, and any elevated CKs prior to the accident would eliminate the resultant spastic hemiparesis and muscular degeneration and damage as potential culprits. CK levels can increase with trauma and physical activity. Your patient’s levels are too high to be ascribed solely to this, but it should also be noted that African-American males have a higher normal range of CK levels than other groups.

I would measure levels of other enzymes derived from muscle, such as aldolase, alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase. Your patient should be evaluated for chronic alcoholism and cocaine use, and his thyroid-stimulating hormone should be measured, as hypothyroidism can result in a myopathy and decreased clearance of CK-MB. Assuming he has no evidence of myopathy or connective tissue disease, other possible etiologies for his chronic CK and CK-MB elevations include being heterozygous for a metabolic myopathy, such as glycogen storage diseases; “presymptomatic” myopathy (where weakness will eventually develop); predisposition to malignant hyperthermia; or macro CK. Macro CK is particularly likely if CK levels have been consistently elevated and there are no other laboratory abnormalities and no obvious clinical explanation. For more information, see Clin Chem. 1986;32:2044-2051.
—Susan Kashaf, MD, MPH (99-15)

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