Hereditary angioneurotic edema: immunochemical 'activity' without clinical expression.

An 11-year-old white female with focal glomerulonephritis was found to have an absence of functional C1 esterase inhibitor. C1 esterase inhibitor measured by immunochemical means, however, was only slightly reduced. After an initial time period marked by variable hypocomplementemia, presumably due to immune complex formation associated with the nephritis, immunochemical signs of active and severe hereditary angioneurotic edema (HANE) developed. These have been unremitting for 3 1/2 years. Clinical signs of HANE, however, have never developed. Thus, during this time, there have been no clinical abnormalities despite the fact that free C1 esterase activity has been persistently present in this patient's serum and serum levels of functional C1 esterase inhibitor, C2 and C4 have been continuously less than 2% of normal. It appears, therefore, that this patient has an unusual form of HANE mainifested solely by the complement alterations seen during symptomatic attacks but without clinical expression of that serologic activity.