C1 INHIBITOR AND DIAGNOSIS OF HEREDITARY ANGIOEDEMA IN NEWBORNS

Symptoms of hereditary angioedema may present during the child's first years. Attacks may be a particular threat to the narrower airway of t he child. An early diagnosis is most valuable because effective C1 inh ibitor (C1 INH) concentrate is available. We present a reference area for the antigenic and functional determination of C1 WH by using uncon taminated umbilical cord blood from 80 normal newborns collected by pu ncturing vessels in the newly delivered placenta. We examined two full -term babies (1 and 2) from mothers with hereditary angioedema type I the same way. The concentration of C1 INH antigen was determined by ra dial immunodiffusion. The C1 INH functional assay was based on the add ition of a known quantity of Cls, which enzymatically splits a chromog enic substrate. The test was performed in the presence of methylamine and heparin in a kinetic microtiter plate assay. Citrated plasma was u sed in both assays. The data obtained in the 80 cord blood samples (25 -97.5 percentile) were 0.11-0.22 g/L for C1 INH antigen (adults, 0.15- 0.33 g/L) and 47.2-85.9% for C1 INH function (percentage of adults). I n cord blood, baby I had an antigenic value of 0.12 g/L (7.5 percentil e) and C1 INH function of 61.8% (42 percentile). The corresponding val ues for baby 2 in cord blood were less than 0.05 g/L (0.106 g/L < 2.5 percentile) and 34.3% (12.9% < 2.5 percentile). Baby 2 had markedly lo wer C4 values yet much higher C4 activation products than baby 1. At 4 mo, baby 1 had an antigenic C1 WH value of 0.24 g/L. At 6 mo, baby 2 had an antigenic value of 0.13 g/L, which is considerably low for the age. At 19 mo of age this child had abdominal pain, distension, and ma ssive amounts of watery diarrhea. CI INH concentrate (500 U) was admin istered, and 4 wk of symptoms resolved within 6 h. This work supports the assumption that the diagnosis of hereditary angioedema can be made at delivery by assessing C1 INH antigen and function.