Which of the following enzyme patterns is MOST diagnostic of Duchenne-type muscular dystrophy?

• A. Total CK level that is 5 to 10 times the ULN
• B. Total CK level that is 25 times the ULN
• C. Total CK level that is 50 to 100 times the ULN
• D. Total CK level that is 1,000 times the ULN

Answer: (C)

Muscle fiber breakdown releases a lot of creatine kinase into the blood, and in Duchenne muscular dystrophy this release is extreme because ongoing muscle degeneration begins in childhood. That leads to CK levels that are far higher than normal, much higher than what you’d see with milder muscle injury or other conditions.

Among the patterns listed, a CK elevation in the very high range—much higher than normal but not the extreme spike seen in some acute injuries—is the most characteristic for Duchenne. This level reflects the persistent, widespread muscle damage that occurs in this disease and helps set it apart from other situations where CK might be only mildly or moderately raised.

Smaller elevations, such as modestly increased CK, can occur with exercise, inflammatory or mild myopathies, or recent strain, and don’t point specifically to Duchenne. An extremely large spike (as with acute, severe muscle injury) is less typical of a chronic dystrophy like Duchenne and more indicative of an acute process.