[A case of Felty's syndrome with marked thrombocytopenia and severe hypocomplementemia].

Felty's syndrome is diagnosed when a patient shows both splenomegaly and leukocytopenia of various degree during the course of rheumatoid arthritis (RA). The accompanying immunologic abnormalities (e.g., antinuclear antibody, antiplatelet antibody, and hypocomplementemia) also characterize Felty's syndrome, but some authors may regard these abnormalities as a transitional form into overlap syndrome [RA + systemic lupus erythematosus (SLE)]. Here we reported a female case of Felty's syndrome who showed marked thrombocytopenia and severe hypocomplementemia. Thrombocytopenia had been refractory against several forms of therapies including high-dose methylprednisolone. Simultaneously, she had various autoantibodies (i.e., antiplatelet antibody, positive Coombs' test, antithyroglobulin antibody, antimicrosome antibody and anti-RNP antibody). Although she did not fulfill the ARA diagnostic criteria for SLE, the degree of thrombocytopenia as well as that of hypocomplementemia argued in favor of the overlap of SLE in this patient. Low-dose cyclosporin A (CsA) combined with small dose of prednisolone could increase both platelet count and level of complement. Notably, the titers of several autoantibodies dropped after CsA was started. These findings might suggest that CsA could normalize the underlying immunologic abnormalities in this patient. However, the disease activity of RA could not be decreased without a help of low-dose methotrexate.