What condition is characterized by RA, joint swelling, enlarged spleen, and leukopenia?

The condition characterized by rheumatoid arthritis (RA), joint swelling, enlarged spleen (splenomegaly), and leukopenia is Felty's syndrome. Felty's syndrome is a rare complication of rheumatoid arthritis that presents with these specific symptoms.

In this syndrome, the combination of RA and an enlarged spleen is associated with a reduction in white blood cell count, specifically leukopenia, which can lead to increased susceptibility to infections. The splenomegaly occurs due to the extra-medullary hematopoiesis or increased destruction of blood cells in the spleen. This triad of symptoms makes Felty's syndrome distinct from other options listed.

Systemic lupus erythematosus could involve joint swelling and hematologic abnormalities, but it does not typically present with splenomegaly and leukopenia exclusively in the way characterized by Felty's syndrome. Gout primarily involves acute episodes of joint inflammation due to crystal deposition, and ankylosing spondylitis is mainly characterized by spinal involvement and does not present with these systemic hematological features. Thus, Felty's syndrome is the most accurate diagnosis for the symptoms described in the question.