## **Core Concept**
Duchenne's muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and weakness. It primarily affects skeletal muscles and is caused by a mutation in the dystrophin gene, leading to the absence of dystrophin protein. This protein is crucial for muscle function and protection.

## **Why the Correct Answer is Right**
The correct answer, **proximal muscle group**, is right because Duchenne's muscular dystrophy predominantly affects the proximal muscles, which are those closer to the trunk of the body. This includes muscles in the pelvis, thigh, and shoulder regions. The absence of dystrophin leads to muscle fiber damage and necrosis, particularly in these areas, resulting in the characteristic muscle weakness and wasting.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because Duchenne's muscular dystrophy does not specifically target distal muscle groups as its primary site of weakness. Distal muscles are those farther away from the trunk of the body.
- **Option B:** This option might seem plausible but is not specific enough in the context of DMD. While DMD does affect various muscle groups, specifying "all of the above" does not accurately reflect the primary distribution of muscle weakness.
- **Option C:** This option is incorrect because it suggests that Duchenne's muscular dystrophy affects only the distal muscle groups, which contradicts the established fact that it primarily affects proximal muscles.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl for Duchenne's muscular dystrophy is the **Gower's sign**, which is a classic clinical feature. It is characterized by the use of hands to "walk" up the thighs to stand up from a prone position, indicative of proximal muscle weakness. Early recognition of such signs can lead to prompt genetic testing and intervention.

## **Correct Answer:** . Proximal muscle group