Which statement correctly describes Duchenne muscular dystrophy?

Which statement correctly describes Duchenne muscular dystrophy?

• A. Autoimmune attack on acetylcholine receptors
• B. Chronic inflammation of joints
• C. A muscular dystrophy due to absence of a sarcolemma-maintaining protein
• D. Overgrowth of skeletal muscle

Answer: (C)

Duchenne muscular dystrophy occurs because a sarcolemma-stabilizing protein, dystrophin, is absent. Dystrophin normally anchors the muscle fiber cytoskeleton to the surrounding extracellular matrix through the dystrophin–glycoprotein complex, providing mechanical stability to the sarcolemma during contraction. Without dystrophin, membranes tear with use, calcium rushes in, proteolytic enzymes are activated, and muscle fibers degenerate. This leads to progressive weakness and replacement of muscle with fibrous and fatty tissue, often with pseudohypertrophy of the calves and early onset in boys due to an X-linked recessive mutation in the DMD gene. A milder form, Becker muscular dystrophy, has some dystrophin function remaining. Other options describe different conditions: an autoimmune attack on acetylcholine receptors is characteristic of myasthenia gravis; chronic joint inflammation points to inflammatory arthritis; and true overgrowth of skeletal muscle would imply hypertrophy, not the degeneration seen in Duchenne.

Duchenne muscular dystrophy occurs because a sarcolemma-stabilizing protein, dystrophin, is absent. Dystrophin normally anchors the muscle fiber cytoskeleton to the surrounding extracellular matrix through the dystrophin–glycoprotein complex, providing mechanical stability to the sarcolemma during contraction. Without dystrophin, membranes tear with use, calcium rushes in, proteolytic enzymes are activated, and muscle fibers degenerate. This leads to progressive weakness and replacement of muscle with fibrous and fatty tissue, often with pseudohypertrophy of the calves and early onset in boys due to an X-linked recessive mutation in the DMD gene. A milder form, Becker muscular dystrophy, has some dystrophin function remaining.

Other options describe different conditions: an autoimmune attack on acetylcholine receptors is characteristic of myasthenia gravis; chronic joint inflammation points to inflammatory arthritis; and true overgrowth of skeletal muscle would imply hypertrophy, not the degeneration seen in Duchenne.