**Question:** Pfropf's Syndrome

**Core Concept:** Pfropf's Syndrome is a rare autoimmune disorder characterized by the presence of immune complexes in the synovial fluid. It is associated with joint pain, swelling, and destruction.

**Why the Correct Answer is Right:** Pfropf's Syndrome is caused by the deposition of immune complexes in the synovial fluid of joints. These immune complexes activate the complement system and lead to synovial inflammation and cartilage and bone destruction. The correct answer, **C**, refers to the autoimmune aspect of the disease, implying that it is an autoimmune disorder where the immune system attacks the body's own tissues, in this case, the joints.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Autoimmune Disorder):** While it is true that Pfropf's Syndrome is an autoimmune disorder, it does not encompass the specific nature of the disease.

B. **Option B (Immune Complex Deposition):** Although immune complex deposition plays a role in Pfropf's Syndrome, this option is too broad and does not address the autoimmune aspect of the disease.

D. **Option D (Destruction of Joints):** While joint destruction is a consequence of Pfropf's Syndrome, this option does not focus on the autoimmune aspect and the immunological mechanism behind the disease.

**Clinical Pearl / High-Yield Fact:**

Pfropf's Syndrome is a rare autoimmune disorder with a prevalence of 0.01% of all rheumatic diseases. It is often misdiagnosed as rheumatoid arthritis. Early diagnosis and treatment are essential to prevent joint deformity and destruction.

**Correct Answer:** C (Autoimmune Disorder)

**Explanation:** Pfropf's Syndrome is an autoimmune disorder characterized by the presence of immune complexes in the synovial fluid, leading to inflammation and cartilage and bone destruction. The correct answer, "Autoimmune Disorder," highlights the autoimmune aspect of the disease, which is crucial for understanding the pathophysiology and appropriate treatment strategies. In Pfropf's Syndrome, the immune system mistakenly attacks the body's own tissues, in this case, the joints. This results in inflammation and joint destruction.