[Acquired C1-esterase inhibitor deficiencies during lymphoid syndromes].

Very marked abnormalities of the complement system were discovered in two patients suffering from a lymphoid syndrome and an IgM 7S dysglobulinaemia. The abnormalities in the complement system were related to a deficiency in C1-estérase (C1 INH). Several findings suggest that such a deficiency is acquired, in particular the absence of any family history of angio-neurotic oedema and, above all, the detection of a marked fall in levels of the C1 fraction which does not exist in the congenital form of deficiency of the inhibitor. The IgM 7S immunoglobulins found in the serum of both patients are probably responsible for the abnormalities in the complement system observed. Such acquired deficiencies in C1 INH are extremely rare since only a few cases have been reported in the literaute, in particular two cases in patients with lymphosarcoma with a serum IgM 7S.