How is DMD typically confirmed at the molecular level?

• A. Genetic testing of the DMD gene with deletion/duplication analysis and sequencing as needed
• B. Muscle biopsy showing dystrophin absence
• C. Serum CK measurement alone
• D. Karyotyping

Answer: (A)

Identifying mutations in the DMD gene is how Duchenne muscular dystrophy is confirmed at the molecular level. The DMD gene is large and can harbor many different mutation types, with deletions or duplications being the most common, and small mutations also possible. The best approach is comprehensive genetic testing of the DMD gene: start with deletion/duplication analysis across the gene, then use sequencing to detect smaller mutations if no deletion or duplication is found. A pathogenic mutation identified in the DMD gene confirms the diagnosis, informs carrier risk for family members, and guides counseling and management options. Muscle biopsy showing absence of dystrophin is informative historically but invasive and less definitive for confirming the genetic cause, while serum CK elevation is sensitive but not diagnostic, and karyotyping does not detect DMD since the issue is a gene mutation, not a chromosomal abnormality.