**Core Concept**
Myositis ossificans progressiva, also known as Fibrodysplasia ossificans progressiva (FOP), is a rare genetic disorder characterized by the abnormal formation of bone tissue in muscles, tendons, and other soft tissues. This condition is caused by a mutation in the ACVR1 gene, which encodes a receptor for bone morphogenetic proteins (BMPs).

**Why the Correct Answer is Right**
In FOP, the abnormal activation of the BMP signaling pathway leads to the formation of heterotopic ossification, where bone tissue forms in non-osseous tissues such as muscles. This process occurs due to the aberrant expression of BMP receptors, particularly ACVR1, which triggers a cascade of events resulting in the activation of osteoblasts and the deposition of bone matrix. The resulting bone formation can lead to significant morbidity and disability.

**Why Each Wrong Option is Incorrect**
**Option A:** Not applicable, as there is no mention of a different condition or mechanism.
**Option B:** This option is incorrect because myositis ossificans progressiva is not caused by a viral infection, but rather by a genetic mutation.
**Option C:** This option is incorrect because scleroderma is a different autoimmune disorder that affects the skin and other organs, and is not related to the abnormal bone formation seen in FOP.

**Clinical Pearl / High-Yield Fact**
FOP is characterized by a distinctive "torch and sword" appearance of the fingers and toes, due to the premature fusion of the epiphyses and the formation of abnormal bone tissue.

**Correct Answer:** C. Scleroderma