What diagnostic test is most definitive for identifying a specific muscular dystrophy subtype?

• A. Genetic testing to identify causative mutations
• B. Serum CK elevation
• C. Muscle biopsy histology
• D. Electromyography

Answer: (D)

Genetic confirmation of the causative mutation identifies the exact muscular dystrophy subtype. Each subtype is defined by a specific gene and mutation, so sequencing panels or broader genetic testing can pinpoint the precise diagnosis, guiding prognosis and potential therapies or trials.

Electromyography can reveal a myopathic pattern and help distinguish myopathy from neuropathy, but it does not reveal the underlying genetic defect or specify the subtype, since many dystrophies share similar EMG features. Serum CK indicates muscle damage but isn’t subtype-specific, and muscle biopsy with histology or protein staining can suggest certain disorders yet often lacks the definitive precision of genetic testing.