Severe and transient pancytopenia associated with a chronic arenavirus infection.

A so-called 'docile' strain of Lymphocytic Choriomeningitis Virus (LCMV) lacks the ability to cause the fatal central nervous system syndrome, commonly associated with most other strains of this virus, in C3HeB/FeJ mice. Hematological evaluation during a 5 week period revealed that every mouse experienced a pancytopenia which was the most severe around three weeks post-infection. The abnormal red blood cell (RBC) morphology seen in the peripheral blood along with the increased reticulocyte count and marked erythroid hyperplasia in the bone marrow indicated peripheral destruction, rather than stem cell inhibition, as the mechanism causing the anemia. An increase in the 59Fe uptake into the blood confirmed the fact that there was no loss in the erythropoietic capabilities in these mice at this time. Although it was clear that the RBCs were being destroyed in the periphery, there was no evidence of a microangiopathic hemolytic anemia nor of a direct viral infection of these cells. Cyclophosphamide treatment, however, prevented the phenomenon. Thus, it seemed likely that the virus-induced hemolytic anemia in these mice was immune-mediated. The late, but not the early drop in the white blood cell counts and the thrombocytopenia, on the other hand, could be traced to granulocyte and megakaryocyte inhibition in the bone marrow.