583 AUTOIMMUNE PANCYTOPENIA IN IDENTICAL TWINS WITH SINUS HISTIOCYTOSIS

Abstract

Eight-year old black male identical twins have similar 4½-year histories of lymphadenopathy and hepatosplenomegaly. Initial lymph node biopsies showed reactive hyperplasia, but more recent biopsies are diagnostic of sinus histiocytosis with massive lymphade nopathy, as described by Rosai and Dorfman. Initial hematologic and immunologic parameters were normal except for polyclonal gammopathy, but both boys subsequently developed mild pancytopenia (neutrophils 200-1000/μl ,platelets 50-150,000/μl ,Hct 27-32%) with hypercellular bone marrows. One has developed corticosteroid-responsive episodes of severe thrombocytopenia (platelets 4,000/μl) and symptomatic hemolytic anemia (Hct 20%). Both boys have positive direct antiglobulin tests and demonstrable anti-platelet and anti-neutrophil antibodies in their sera, suggesting that their pancytopenia is immunologically mediated. Antinuclear antibody is absent. Circulating T-cell numbers assessed by E rosettes are depressed, but there are no identifiable abnormalities in number of B-cells or in responsiveness of their lymphocytes to mitogens. Family history is negative and there have been no known exposures to toxic infectious or chemical agents. However, Ebstein-Barr virus antibody titers are markedly elevated in both boys. These patients appear unique since sinus histiocytosis has not previously been described in siblings or in association with a possible immunoregulatory defect leading to immune-mediated blood cell destruction.

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