A study of some complement functions was performed in two patients affected with hereditary angioneurotic edema (HAE) – mother and daughter – from a Southern Italy family (Apulia) and in three of their relatives. A decreased level of the C1 esterase plasma inhibitor was found in both the patients, who were treated with tranexamic acid with a slight, but definite improvement. However, the disease could not be traced beyond two generations in the pedigree and a couple of ascendants was found who were free from HAE both from the clinical standpoint and from that of the laboratory evaluation of complement functions. The possibility that HAE arose in the family through a mutational event is discussed.
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