The Felty syndrome is the triad of rheumatoid arthritis, splenomegaly, and neutropenia. The use of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in patients with the Felty syndrome has yielded variable results [1, 2]. This is the second reported application of rG-CSF in a patient with the Felty syndrome [3].

A 51-year-old white man with seropositive rheumatoid arthritis and absolute neutrophil counts ranging from 0.055 to 0.2 x 10⁹/L for 10 years was referred for frequent sinopulmonary and skin infections. Examination showed splenomegaly and stigmata of rheumatoid arthritis; bone marrow examination was hypercellular with a left-shifted myeloid line consistent with the Felty syndrome. Oral methotrexate, 2.5 mg, was given thrice weekly for 2 months without effect and was discontinued.

Recombinant G-CSF was begun at 5 µg/kg per day subcutaneously and was later increased to 10 µg/kg per day. Hemoglobin and platelets fell during the next 3 weeks, and G-CSF was stopped (Figure 1). Direct Coombs test, antiplatelet antibodies, and serial stool guaiacs were negative; lactate dehydrogenase and indirect bilirubin values were normal. Craniocaudal spleen span was 17.3 cm by ultrasound, without evidence of a bleed or infarct. A repeat ultrasound on day 60 showed a spleen span of 13.9 cm, and bone marrow was unchanged.

View larger version (28K): [in this window] [in a new window]   Figure 1. Lipid profile in a 36-year-old man treated with -interferon for chronic hepatitis C. IF = interferon; TG = triglycerides.

The optimal treatment of symptomatic Felty syndrome is undefined. The use of rGM-CSF, although leading to increased neutrophils, has been associated with an arthritic flare [2]. A patient treated with G-CSF had a significant increase in neutrophils while receiving 5 µg/kg per day [3]; however, an allergic skin reaction required discontinuation of the drug. Our patient showed no evidence of bleeding, hemolysis, or autoimmune consumption. Treatment with rG-CSF has not been shown to affect erythroid cells [4]. A transient and less striking thrombocytopenia has been reported with rG-CSF [5] but at doses higher than those used here. Acute splenic sequestration was possible, given the apparent transient increase in the size of the spleen. A "steal" phenomenon might have occurred with increased myeloid progenitors at the expense of erythroid and megakaryocytic elements.

Resolution of the cytopenias after discontinuation of rG-CSF suggests a causative role. Caution is warranted in the use of rG-CSF in patients with the Felty syndrome.