Felty syndrome is the triad of rheumatoid arthritis, splenomegaly and neutropenia (neutrophils under 2.0 x 10^9/L).

Occurs in under 1% of rheumatoid arthritis patients, usually in long standing, seropositive, erosive disease, in white patients aged 50 to 70, with HLA-DR4.
Neutropenia from antineutrophil antibodies, immune complexes, impaired granulopoiesis and splenic sequestration; may coexist with large granular lymphocyte leukaemia.
Complications: recurrent bacterial infections (skin, respiratory), leg ulcers, vasculitis, lymphoma.

Full blood count with persistent neutropenia, rheumatoid factor and anti-CCP strongly positive, ANA positive in 60%.
Exclude drug-induced neutropenia (methotrexate, sulfasalazine, gold, penicillamine), LGL leukaemia (flow cytometry, T cell receptor rearrangement), MDS, infection, B12/folate deficiency.
Ultrasound or CT for spleen size; bone marrow if cytopenias unexplained.
Immunoglobulins, hepatitis, HIV.

Treat the rheumatoid arthritis: methotrexate 7.5 to 15 mg weekly (neutropenia may improve, monitor closely), often first line.
Alternatives: rituximab 1 g on days 1 and 15, leflunomide 20 mg daily (monitor counts), ciclosporin 2.5 to 5 mg/kg, azathioprine 1 to 2 mg/kg, sulfasalazine cautiously; TNF inhibitors have been used.
Recurrent infection with severe neutropenia (under 0.5 x 10^9/L): filgrastim 5 micrograms/kg SC daily or 300 micrograms three times weekly until count recovers.
Splenectomy for refractory neutropenia with serious infection (response in 80%, relapse possible, vaccinate beforehand with penicillin prophylaxis).
Short course prednisolone 20 to 40 mg for acute neutropenia.
Prompt treatment of fever: broad spectrum antibiotics (piperacillin tazobactam 4.5 g every 6 hours).
Monitor counts weekly initially, then monthly; vaccinations.

Felty Syndrome

Overview