Case Presentation: A 56 year old female patient with past medical history of hypertension and diabetes mellitus type 2 presents to the emergency department with a 1 day history of fever and confusion. Vitals showed a temperature of 101.4 F, heart rate at 112 beats per minute, blood pressure at 136/73. Initial lab work was notable for leukopenia of 2.1 x10^3/uL, with an absolute neutrophil count of 191, hemoglobin of 5.3 g/dL, and platelets at 120 x10^3/uL. Head imaging was unremarkable. Physical exam was notable for splenomegaly. Chart review showed two previous bone marrow biopsies ordered due to pancytopenia, first in 02/2018, notable for “reactive bone marrow,” and a second bone marrow biopsy in 11/2019 that was negative for abnormal cell populations.Patient was admitted, treated with antibiotics empirically for neutropenic fever. Blood cultures and infectious work up was negative. Rheumatological work up was pursued, and was notable for an elevated rheumatoid factor at 190.9 IU/mL, elevated anti-CCP at 178 units, ANA titer of 1:640, and low C3. Additional work up including C4, hepatitis panel, ADAMTS13, CMV, EBV, HHV6, and parvovirus were negative. CT imaging was pursued and showed a spleen of 19.88 cm in craniocaudal axis [Figure 1]. Flow cytometry showed an atypical T-cell population. Differential at this time included Felty’s syndrome and large granular lymphocytic leukemia. Oncology service was consulted, bone marrow biopsy and myelodysplastic syndrome panel were pursued and did not show an underlying malignancy. Patient’s fevers subsided, confusion resolved, and G-CSF was given. Patient’s neutrophil count recovered, fevers resolved, and patient was discharged on prednisone and methotrexate. Patient was re-admitted one month later with neutropenia and fever. Splenectomy was performed and patient’s white blood cells recovered in the subsequent months. No further episodes of neutropenia have occurred since.

Discussion: Felty’s syndrome is characterized by the triad of neutropenia, splenomegaly, and rheumatoid arthritis. It typically presents late in the course, roughly in 1% of patients, with patients having at least 20 years of rheumatoid arthritis [1] prior to presentation. Neutropenia is multifactorial and, like in our case, can be the presenting symptoms. An immune component is suspected, with some having antibodies against G-CSF, and a relationship to HLA-DR4 [1,2]. Large granular lymphocytic leukemia also shares HLA-DR4, and should be evaluated with flow cytometry, bone marrow biopsy, and myelodysplastic syndrome panel. Splenomegaly also contributes to neutropenia, due to sequestration and peripheral destruction of neutrophils [3]. The mainstay treatment are disease-modifying antirheumatic drugs. Splenectomy can be performed if disease-modifying antirheumatic drugs are not effective at treating the neutropenia.

Conclusions: Felty’s syndrome is diagnosed clinically with the triad of neutropenia, splenomegaly and RA. FS should be considered in all patients presenting with any symptom of the classic triad, particularly if there are physical findings to suggest a history of inflammatory arthritis. It is important to keep a broad differential regarding neutropenic fever, and to consider Felty’s syndrome if splenomegaly or seropositive rheumatoid arthritis findings are present.

IMAGE 1: Figure 1: Spleen measured at 19.88 cm in craniocaudal axis