Pseudo Felty's syndrome (PFS) is an uncommon syndrome occurring in Rheumatoid Arthritis and characterized by a monoclonal expansion of lymphocytes with neutropenia. Methotrexate is the first line recommended treatment. In case of incomplete response, cyclophosphamide may be used for hematological features but does not share the same efficacy on arthritis. We investigate the effect of rituximab in PFS as second line treatment.

This is a retrospective study about six cases of PFS treated with methotrexate and/or rituximab.

Five women and 1 man (mean age: 66years) were included. All patients were positive for rheumatoid factor and five were anti CCP positive. All patients presented bone erosions, three had splenomegaly. The disease duration was between 0 and 19years at large granular lymphocyte (LGL) leukemia diagnosis. Methotrexate was effective and well tolerated for two patients with a follow up of 7 and 4years. For a third patient, the hematological symptoms were predominant and he received after methotrexate, several infusions of cyclophosphamide. Three patients (2 T-cell and 1 NK-cell LGLL) were treated with rituximab (two 1000mg infusions) with a decreased DAS28 and an increased neutrophil count, with subsequent courses of rituximab one to three years later with the same efficacy. This treatment was well tolerated without infectious events after a follow up of one and three years.

Methotrexate is effective in near half of cases of PFS. In second line, rituximab may be a therapeutic option with good efficacy and tolerance.