A 5-year-old boy has progressive proximal muscle weakness, Gowers sign, and calf pseudohypertrophy. Serum creatine kinase is 12,000 U/L. His mother is asymptomatic. What is the mode of inheritance?

• A Autosomal dominant
• B Autosomal recessive
• C Mitochondrial
• D X-linked recessive ✓

Explanation

Duchenne muscular dystrophy is X-linked recessive, caused by dystrophin gene mutations. Males are affected; females are typically asymptomatic carriers. The very high CK, calf pseudohypertrophy, and Gowers sign are characteristic. Autosomal dominant or recessive patterns would not explain the asymptomatic mother with an affected son.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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