**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation and degeneration of the joints, leading to various systemic manifestations. The extra-articular features of RA are due to the systemic effects of the disease and the deposition of immune complexes in various organs.

**Why the Correct Answer is Right**
Proteinuria is not a characteristic feature of rheumatoid arthritis. In contrast, other extra-articular manifestations such as pleural effusion, conjunctivitis, and weight loss are commonly seen in RA patients. The systemic inflammation and immune complex deposition in RA lead to the development of these extra-articular features.

* **Option A:** Weight loss is a common feature of RA due to chronic inflammation and the catabolic effects of cytokines such as TNF-alpha.
* **Option B:** Pleural effusion is a manifestation of RA due to the deposition of immune complexes in the pleural space, leading to inflammation and fluid accumulation.
* **Option C:** Conjunctivitis is a common ocular manifestation of RA, resulting from the deposition of immune complexes in the conjunctiva and the subsequent inflammation.

**Clinical Pearl / High-Yield Fact**
Extra-articular features of RA can be divided into three main categories: pulmonary (pleural effusion, pneumonitis), ocular (conjunctivitis, scleritis), and hematologic (anemia, leukopenia).

**✓ Correct Answer:** D. Proteinuria