[Acquired C1 esterase inhibitor deficiency and lymphoproliferative syndromes]

About 20 cases of acquired C1 esterase inhibitor deficiency have been reported in association with malignant lymphomas. We describe 3 such patients. The 3 patients studied were asymptomatic and had low C1q level. Danazol administration resulted in an increase of C1 esterase inhibitor in 2 patients. The complement activation in acquired C1 esterase inhibitor deficiency could be explained by interaction with pathological cells of the spleen, the blood or the bone-marrow. The mechanism of decrease of C1 INH is discussed.