Disseminated Histoplasmosis Mimicking Felty's Syndrome

The successful treatment of rheumatoid arthritis often requires the use of immunosuppressive medications. Although these agents have different potential toxicities, they share in common the potential for permitting the development of opportunistic infections. We describe 2 patients with chronic rheumatoid arthritis treated with immunosuppressive agents who developed progressive neutropenia with documented splenomegaly. The differential diagnosis included Felty's syndrome versus bone marrow suppression from their immunosuppressive medication. Although both patients had the triad of Felty's syndrome, high titer seropositive rheumatoid arthritis with splenomegaly and neutropenia, the diagnosis of this syndrome relies on excluding other potential causative factors. Further investigation revealed that both patients had disseminated histoplasmosis with bone marrow involvement, which most likely represented reactivation from prior exposure to Histoplasma capsulatum. Opportunistic infections such as disseminated histoplasmosis can mimic other disease processes, including Felty's syndrome, and are important to consider when there is a change in the clinical status of patients with rheumatic disease who are immunocompromised.