Small bowel angioedema due to acquired C1 inhibitor deficiency: a case report and overview.

Acquired angioedema is a rare disorder caused by an acquired deficiency of C1 inhibitor. It is characterized by nonpitting, nonpruritic subcutaneous or submucosal edema of the skin, or of the respiratory or gastrointestinal tract. When localized in the gastrointestinal tract, it can cause severe abdominal pain, mimicking an acute surgical abdomen, or chronic recurrent pain of moderate intensity. We report a case of a 48-year-old man presenting with recurrent episodes of hypotension and abdominal pain. Computed tomography of the abdomen showed edema of the small bowel. The first determinations of C1 inhibitor level and activity, measured in a symptom-free period, were normal. Repetition of the laboratory tests in the acute phase, however, showed a low C1 inhibitor level. Further diagnostic work-up indicated an acquired C1 inhibitor deficiency caused by a monoclonal gammopathy. He was treated with tranexamic acid as prophylaxis for his frequent attacks and to date, he has remained symptom free. Acquired C1 inhibitor deficiency is a rare cause of angioedema and is, among others, related to autoantibodies and abnormal B-cell proliferation, for example monoclonal gammopathy. The diagnosis of acquired C1 inhibitor deficiency is made on the basis of the medical history and on the level and activity of plasma C4, C1q, and C1 inhibitor. In case of high suspicion and a normal C1 inhibitor activity, it is recommended to repeat this test during an angioedema attack. Early diagnosis is important for the treatment of severe, potentially life-threatening attacks and to start prophylactic treatment in patients with frequent or severe angioedema attacks.