What is the most common fatal muscular dystrophy beginning in early childhood, and what is its inheritance pattern?

• A. Duchenne muscular dystrophy (DMD) with X-linked recessive inheritance
• B. Becker muscular dystrophy (BMD) with X-linked recessive inheritance
• C. Myotonic dystrophy type 1 with autosomal dominant inheritance
• D. Facioscapulohumeral muscular dystrophy with autosomal dominant inheritance

Answer: (A)

Duchenne muscular dystrophy is the most common fatal muscular dystrophy that begins in early childhood. It results from mutations in the dystrophin gene on the X chromosome, causing little or no dystrophin protein in muscle membranes. Without dystrophin, muscle fibers are easily damaged, leading to rapid proximal weakness, Gowers’ sign when standing, and calf pseudohypertrophy. The inheritance is X-linked recessive, so affected males usually inherit the mutation from carrier mothers and are affected, while carrier females are typically asymptomatic; affected males pass the mutation to all daughters (carriers) and to no sons, explaining the pattern seen in this condition. This fits the early-onset, progressive, and often fatal course best compared with the other options.