**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by symmetric polyarthritis, leading to inflammation and joint damage. In RA, the immune system produces autoantibodies, including rheumatoid factor (RF), which is a marker of disease activity. The condition can also lead to cytopenias due to bone marrow suppression.

**Why the Correct Answer is Right**
The patient's laboratory values and clinical presentation are consistent with rheumatoid arthritis. The presence of rheumatoid factor titer of 1:4096 indicates active disease. In RA, the immune system suppresses the bone marrow, leading to a decrease in white blood cell count. The differential count is expected to show a decrease in mature granulocytes, such as neutrophils and eosinophils, due to bone marrow suppression.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is unlikely for RA to cause an increase in white blood cell count. While some patients may have a mild increase in WBC, it is not a characteristic feature of RA.
* **Option B:** This option is incorrect because RA does not typically cause an increase in lymphocytes. While lymphocytes may be present in the synovial fluid, the overall WBC count is typically decreased due to bone marrow suppression.

**Clinical Pearl / High-Yield Fact**
RA can lead to significant morbidity if not treated promptly. The presence of rheumatoid factor and symmetrical polyarthritis should prompt a diagnosis of RA, and treatment should be initiated to prevent joint damage and other complications.

**Correct Answer: D.**