A young adult presents with proximal weakness of upper limbs, features of facial palsy and winging of scapula. The most likely diagnosis is:
**Core Concept**
The patient's presentation is suggestive of a neuromuscular disorder affecting the proximal muscles of the upper limbs, facial muscles, and muscles of the shoulder girdle. This condition is characterized by weakness, wasting, and degeneration of the affected muscles.
**Why the Correct Answer is Right**
The most likely diagnosis is Duchenne Muscular Dystrophy (DMD), a genetic disorder caused by mutations in the dystrophin gene. DMD leads to the production of a defective dystrophin protein, which is essential for muscle function and maintenance. The absence or dysfunction of dystrophin results in progressive muscle degeneration, particularly affecting the proximal muscles of the upper limbs, facial muscles, and muscles of the shoulder girdle. The winging of the scapula is a result of the weakness of the serratus anterior muscle, which is responsible for scapular stabilization.
**Why Each Wrong Option is Incorrect**
* **Option A:** While polymyositis is an inflammatory muscle disease, it typically presents with symmetrical muscle weakness and does not have a genetic component.
* **Option B:** Myasthenia Gravis is an autoimmune disease characterized by fluctuating muscle weakness, particularly affecting the muscles of the face and eye. However, it does not typically present with winging of the scapula or proximal upper limb weakness.
* **Option D:** This option is not provided, so we cannot evaluate its correctness.
**Clinical Pearl / High-Yield Fact**
DMD is an X-linked recessive disorder, meaning it primarily affects males. Female carriers may exhibit mild symptoms due to X-chromosome inactivation.
**Correct Answer:** C.