Homosexual men with thrombocytopenia have impaired reticuloendothelial system Fc receptor-specific clearance

Classic immune thrombocytopenia purpura (ITP) occurs predominantly in women and is associated with either normal or impaired Fc receptor-mediated clearance of antibody-coated cells. Recently, an increasing incidence of thrombocytopenia has been observed in homosexual men, but whether Fc receptor-mediated clearance of antibody-coated cells is normal or impaired in these men is unknown. To study this question, we measured the in vivo clearance of anti-Rh₀(D) IgG antibody-sensitized ⁵¹Cr-labeled autologous red cells in five homosexual men with thrombocytopenia without an evident cause. All five had antibodies to human immunodeficiency virus, and four had circulating immune complexes as determined by a Clq-binding assay. Two of the men tested also had an increase in platelet-associated IgG. In the four homosexual men with platelet counts of 20,000/μL or less, the clearance half-time of IgG-sensitized red cells was prolonged (mean, 106 minutes; range, 72 to 140 minutes) as compared with the clearance of such cells in five hematologically normal men (mean, 39 minutes; range 30 to 50 minutes; P < .005). One homosexual man with a platelet count of 81,000/μL had a normal clearance half-time (30 minutes). Three patients whose platelet counts increased after corticosteroid therapy were restudied. In all three, the clearance of antibody-coated cells was shortened and returned to normal in the one patient who had achieved a complete remission. No correlation was observed between the presence of platelet-associated IgG or circulating immune complexes and the clearance half-time. These data indicate that severe thrombocytopenia occurring in homosexual men as in some patients with classic ITP is associated with defective in vivo Fc receptor-mediated clearance of antibody-coated cells.