Hypocomplementemia and hematological abnormalities in immunoblastic lymphadenopathy and immunoblastic lymphadenopathy-like T cell lymphoma.

Serum complement levels and hematological data were evaluated in five patients with immunoblastic lymphadenopathy (IBL) and four with IBL-like T cell lymphoma (IBL-T). Anemia with Hb values below 10.0 g/dl was seen in four patients. A direct Coombs test was positive in five patients and the bone marrow of two of these showed features of pure red cell aplasia. Seven patients were thrombocytopenic with platelet counts below 100 x 10(9)/l. Six of the seven patients had splenomegaly. Platelet-associated IgG was elevated in all three thrombocytopenic patients examined. Whole complement activity (CH50) was reduced in eight patients (89%) at presentation and subsequently normalized in five who were treated either with prednisolone (two patients with IBL) or with multidrug combination chemotherapy (three with IBL-T). One patient achieved complete remission and four partial remission. Remission was accompanied by normalization of hematological abnormalities and elevation of complement activity to the normal range in all cases. These results suggested that complement-mediated mechanisms are responsible, at least in part, for some of the hematological abnormalities observed in IBL and IBL-T and that hypocomplementemia is a common abnormality with significance as a laboratory marker for the disease activity.