The enzyme, whose blood levels is increased in patients with Duchenne muscular dystrophy is

The correct option is Creatinine phosphokinase.

Step-by-Step Explanation:

1. Understanding Duchenne Muscular Dystrophy (DMD):
Duchenne muscular dystrophy is a severe, progressive genetic disorder characterized by muscle degeneration and weakness. It is caused by mutations in the gene responsible for producing dystrophin, an essential structural protein that helps keep muscle cells intact. Without functional dystrophin, the muscle cell membranes (sarcolemma) become fragile and tear easily during muscle contraction and relaxation.

2. Consequence of Muscle Membrane Damage:
When the cell membranes of muscle fibers are compromised, intracellular contents and enzymes leak out of the damaged muscle cells directly into the extracellular space and the bloodstream.

3. Role of Creatinine Phosphokinase (CPK):
Creatinine phosphokinase (also known as creatine kinase, CK) is an enzyme found in high concentrations within skeletal muscle, cardiac muscle, and the brain. It plays a critical role in cellular energy metabolism by catalyzing the reversible transfer of phosphate between ATP and creatine. When muscle fibers undergo degeneration and damage, as seen in DMD, massive amounts of CPK leak into the blood.

4. Diagnostic Significance:
Consequently, serum levels of creatinine phosphokinase (specifically the CK-MM isoenzyme variant found in skeletal muscle) are severely elevated in patients with Duchenne muscular dystrophy, often reaching 10 to 100 times the normal limit, making it a key diagnostic marker for the disease.