An antibody cytotoxic to megakaryocyte progenitor cells in a patient with immune thrombocytopenic purpura

Efficacy of danazol in pure red cell aplasia

Twenty-one unselected patients with refractory chronic anemias of various etiologies were treated with danazol, a synthetic attenuated androgen. All had previously failed treatment with hematinics, androgens, corticosteroids, high-dose intravenous immunoglobulin, antithymocyte globulin, cytotoxic immunosuppressive agents, and/or plasmapheresis. Three patients with pure red cell aplasia and one with aplastic anemia responded. No responses were observed in 11 patients with myelodysplastic syndromes, two patients with myelofibrosis, and two with paroxysmal nocturnal hemoglobinuria. Remission in pure red cell aplasia was maintained with danazol alone in one patient and required combined low-dose prednisone in two. Objective responses occurred in 2 to 3 weeks and therapy generally was well tolerated. To date, one patient with pure red cell aplasia remains in complete remission at 9 months on low-dose danazol alone. We conclude that danazol alone or combined with prednisone may induce and maintain remission in severe refractory pure red cell aplasia and possibly other chronic cytopenias characterized by immunologic marrow suppression. Further trials of danazol in treating these disorders are indicated.

Complement-dependent cytotoxic factor to megakaryocyte progenitors in sera from patients with idiopathic thrombocytopenic purpura

The influence of sera from patients with idiopathic thrombocytopenic purpura (ITP) was examined on colony formation from megakaryocyte (M) progenitors. Though incubation of marrow cells in Iscove's modified Dulbecco's medium (IMDM) containing 50% sera from several ITP patients stimulated M-colony formation in 8 of 13 cases, incubation in the sera from the patients and in baby rabbit serum as a source of complement significantly suppressed the colony formation. Experiments showed that sera of immunoglobulin G from ITP patients had significant complement-dependent cytotoxicity to M-progenitors in normal marrow cells or in the marrow cells from corresponding patients, but not to CFU-e, BFU-e or CFU-gm. Cytospin preparations of individually collected M-colonies from marrow cells treated with ITP patients' sera and complement revealed a reduction of megakaryocyte colonies containing cells of multilineages. These results indicate that autoantibodies detected in ITP patients can bind not only to platelets and megakaryocytes, but may also bind to M-progenitors.