Acquired C1 inhibitor deficiency: Clinical manifestations, epidemiology, pathogenesis, and diagnosis

INTRODUCTION — Acquired deficiency of C1 inhibitor (C1-INH), also called acquired angioedema (AAE), is a rare syndrome of recurrent episodes of angioedema, without urticaria, which is associated with B cell lymphoproliferative disorders in some patients [1,2]. Angioedema typically affects the skin or mucosal tissues of the upper respiratory and gastrointestinal tracts. The swelling is self-limited, although laryngeal involvement may cause fatal asphyxiation. Clinically, this disorder is very similar to hereditary angioedema (HAE), although AAE most commonly develops in patients over the age of 40 years, some of whom have associated lymphoproliferative disorders, whereas HAE usually presents in younger patients who are otherwise healthy.