Which statement describes CK levels in Duchenne muscular dystrophy?

• A. Normal CK levels
• B. Elevated CK levels
• C. Reduced CK levels
• D. CK activity absent

Answer: (B)

Muscle membrane damage in Duchenne muscular dystrophy causes leakage of intracellular enzymes into the blood, and creatine kinase is abundant in skeletal muscle. As dystrophin deficiency leads to ongoing muscle fiber breakdown, CK spills into the serum, producing markedly elevated levels. This elevation is a hallmark of muscle injury in DMD and is typically much higher than normal, especially in young affected individuals. So the statement that CK levels are elevated best describes the situation.

Normal CK would not fit the picture of active, ongoing muscle fiber breakdown. Reduced CK or CK activity absent would imply either less muscle breakdown or a CK enzyme deficiency, neither of which characterizes Duchenne.