A 40 year old woman has severe, disabling rheumatoid ahritis. Rheumatoid factor is positive. What would a biopsy of the synovium of her knee most likely reveal?
**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation and hyperplasia of the synovial membrane, leading to joint damage and destruction. The synovium, a thin layer of connective tissue, becomes infiltrated with immune cells and undergoes hypertrophy, resulting in a thickened synovial membrane.
**Why the Correct Answer is Right**
In rheumatoid arthritis, the synovium undergoes a process called pannus formation, where a dense, vascularized, and hyperplastic tissue forms on the surface of the joint. This pannus is composed of lymphocytes, macrophages, and plasma cells, which are characteristic of a chronic inflammatory response. The presence of rheumatoid factor, a type of autoantibody, further supports the diagnosis of RA. The synovial membrane becomes thickened and infiltrated with immune cells, leading to joint damage and destruction.
**Why Each Wrong Option is Incorrect**
**Option A:** A nearly normal synovium with scattered inflammatory cells is not consistent with the chronic inflammatory response seen in RA. The synovium in RA is typically thickened and hyperplastic, with a dense infiltrate of immune cells.
**Option B:** A non-proliferative synovitis with abscess formation is more characteristic of a bacterial infection, such as septic arthritis. RA is an autoimmune disorder, not an infectious process.
**Option C:** A non-proliferative synovitis with many neutrophils is also more characteristic of a bacterial infection, such as septic arthritis. While neutrophils may be present in RA, the synovium is typically proliferative and hyperplastic, with a dense infiltrate of lymphocytes, macrophages, and plasma cells.
**Clinical Pearl / High-Yield Fact**
In RA, the synovial membrane can become so thickened and hyperplastic that it can cause joint destruction and deformity. This is known as pannus formation, and it is a hallmark of the disease. Understanding the pathophysiology of RA is crucial for managing the disease and preventing joint damage.
**✓ Correct Answer: D. A proliferative synovitis with many lymphocytes, macrophages, and plasma cells**