Kavanaugh [1] recently reported the beneficial effect of danazol on thrombocytopenia in a patient with the antiphospholipid antibody syndrome.

We describe a woman with thrombocytopenia associated with primary antiphospholipid syndrome who responded to dapsone therapy. Her medical history included two fetal losses. In December 1993, profound thrombocytopenia (platelet count, 10 x 10⁹/L) was seen with another spontaneous abortion. Treatment with prednisone (80 mg daily) was started, and her platelet count transiently increased to 37 x 10⁹/L. She was hospitalized in our unit in February 1994. Physical examination was unremarkable except for ecchymotic purpura. Prednisone (1 mg/kg body weight) was administered. Laboratory findings included a low platelet count (22 x 10⁹/L), IgG platelet antibodies by direct immunofluorescence test, negative test results for antinuclear factors, and antibodies to native DNA and human immunodeficiency virus (HIV). IgG anticardiolipin antibodies were detected by enzyme-linked immunoassay (65 units; normal, <15 units). Dapsone (75 mg daily) was added to the regimen. One month later, her platelet count had increased to 108 x 10⁹/L, and the dose of prednisone was tapered. The platelet count returned to within the normal range after 3 months of dapsone therapy. After 9 months of follow-up, the patient continues to receive low-dose prednisone (10 mg/d) and dapsone (75 mg/d) without side effects. Her platelet count remains within the normal range. The response of the platelet count to therapy is shown in Figure 1.

Dapsone treatment of autoimmune thrombocytopenic purpura has been reported to be effective, particularly in elderly patients [2] and in patients with HIV-related autoimmune thrombocytopenic purpura [3]. Godeau and colleagues [4] observed a response in 13 of 27 patients with no serious hematologic complications. Dapsone was also beneficial in a patient with thrombocytopenia that was associated with the primary antiphospholipid syndrome [5]. Although this drug affects phagocyte-mediated cytotoxicity [2], the mechanism of dapsone's effectiveness in autoimmune thrombocytopenic purpura remains unknown. Our experience suggests that dapsone may be a beneficial, safe, and inexpensive therapy in thrombocytopenia associated with the antiphospholipid antibody syndrome.