Does Normal or Minimally Decreased Serum C4 Level Exclude the Diagnosis of Hereditary Angioedema?

Ali Kutlu
Ercan Karabacak
Sami Öztürk
Ogün Sezer
Yalçın Önem
Oktay Taşkapan

Abstract

C1 inhibitor deficiency (hereditary or acquired) is characterized by the occurrence of subcutaneous and submucosal swellings in any part of the skin and the respiratory and gastrointestinal tracts. In the hereditary form, symptoms usually appear early in life and normally accompanied by a family history. Serum complement 4 (C4) level is a good screening test for C1 inhibitor deficiency as serum C4 is invariably low in untreated hereditary angioedema (C4 < 30% of mean normal level). All patients who are suspected of having C1 inhibitor deficiency should have a C4 level measured. If C4 is normal it is not usually necessary to proceed to C1 inhibitor analysis. In this report, we present a 27 years old male patient having painful swellings in various part of his skin and submucosal areas with normal or minimally decreased serum C4 levels and clinically benefit from the danazol treatment. We suggest that normal C4 level in an untreated patient may not exlude the diagnosis of hereditary angioedema.

Keywords

Hereditary angioedema, compleman 4, C1 inhibitor deficiency
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