What genetic test is best for confirming a diagnosis in a child with bilateral calf pseudohypertrophy and Gower sign?

The most appropriate test for confirming the diagnosis in this scenario is genetic testing for dystrophin gene deletion. A child presenting with bilateral calf pseudohypertrophy and a positive Gower sign suggests the possibility of Duchenne Muscular Dystrophy (DMD), a genetic disorder characterized by progressive muscle degeneration and weakness. This condition is primarily caused by mutations in the dystrophin gene located on the X chromosome.

Genetic testing is the most definitive method to confirm a diagnosis of DMD, as it can detect deletions, duplications, and point mutations in the dystrophin gene. Detecting a deletion in this gene is particularly significant, as it directly correlates with the pathology underlying the condition. Early diagnosis is critical for managing the disease effectively and providing family counseling, which highlights the importance of this genetic test.

While muscle biopsy and magnetic resonance imaging can provide valuable information regarding muscle pathology and structure, they are not as definitive as genetic testing for confirming DMD. A muscle biopsy may show changes such as fiber degeneration, but it does not identify the specific genetic mutation causing the disorder. Similarly, MRI can visualize muscle changes but lacks the specificity necessary to make a definitive diagnosis. A complete blood count is not relevant in diagnosing muscular dystrophies,