What test is considered the most definitive for establishing the precise muscular dystrophy subtype?

• A. Muscle biopsy
• B. Serum CK measurement
• C. Electromyography
• D. Genetic testing for causative mutations

Answer: (D)

Pinpointing the exact muscular dystrophy subtype comes from identifying the specific genetic change causing the disease. Each subtype corresponds to a particular gene and mutation, and many subtypes can look similar clinically. Genetic testing for causative mutations directly reveals that defective gene, giving a precise subtype classification with high confidence. That’s why it’s the most definitive tool for subtyping.

Other tests show that muscle is affected or damaged—serum CK levels rise with muscle breakdown, electromyography reveals a myopathic pattern, and muscle biopsy shows dystrophic fibers and may show loss of a specific protein on staining—but these findings don’t pinpoint the exact gene involved. Genetic testing, often via targeted panels or broader sequencing, provides the definitive genotype that guides prognosis, counseling, and potential gene-specific therapies or trials.