Massive Splenomegaly in Felty's Syndrome: A Case Report.

Felty's syndrome (FS) is a rare and complex condition most commonly seen as a complication of longstanding rheumatoid arthritis (RA), characterized by a triad of RA, splenomegaly, and neutropenia. Diagnosing FS can be challenging due to its diverse clinical presentations and overlap with other hematologic and autoimmune conditions. We report a 47-year-old male with a history of severe anemia, recurrent blood transfusions, and a chronic leg ulcer. In 2024, he presented with significant weight loss, polyarthralgia, and splenomegaly, prompting concern for a hematologic malignancy. Laboratory findings included elevated beta-2-microglobulin and positive antinuclear antibodies, raising suspicion of lymphoma or other malignancies. Extensive testing ruled out hematologic malignancies and schistosomiasis, and further investigation suggested FS. He was started on prednisone, filgrastim, and methotrexate, leading to substantial clinical improvement, including reduction of joint symptoms, spleen size, and improvement of the leg ulcer. This case highlights the diagnostic complexities of FS, especially in the absence of a prior RA diagnosis. FS should be considered in the differential diagnosis when encountering unexplained splenomegaly and neutropenia, even without a history of chronic RA. Early recognition and treatment can significantly improve patient outcomes. FS, though rare, should be considered in patients presenting with systemic symptoms, cytopenias, and splenomegaly. A thorough diagnostic workup is crucial to differentiate FS from other conditions, particularly hematologic malignancies. This case underscores the importance of prompt diagnosis and treatment to achieve favorable clinical outcomes.