Background: Hereditary angioneurotic edema is characterized by recurrent paroxysms of edema formation involving subcutaneous tissues, as well as the mucosal membrane of the larynx or the gastrointestinal tract.
Case Report: This case report describes edema formation in an uncommon location. A 16-years-old patient developed an acute abdominal attack of hereditary angioneurotic edema, complicated by the appearance of a slit-shaped pericardial effusion. Although hemodynamically insignifi cant, the effusion was evident upon physical examination and was accompanied by ECG changes; however, it resolved completely after C1-inhibitor substitution.
Conclusions: This finding should prompt for extended search after uncommon abnormalities using noninvasive diagnostic modalities available.

Keywords: hereditary angioedema, abdominal attack, pericardiac effusion