Hereditary angioedema (HAE) is a genetic disorder characterized by recurrent episodes of severe swelling of the skin, respiratory tract, and gastrointestinal tract. This condition is associated with a deficiency in which of the following complement regulatory proteins?

Explanation

Hereditary angioedema (HAE) is caused by a deficiency or dysfunction of C1 inhibitor (C1-INH). C1-INH regulates the classical and lectin complement pathways by inactivating C1r, C1s, and MASP-1/MASP-2. Its deficiency leads to uncontrolled activation of these pathways, particularly C2 and C4, and also affects the kinin system, leading to excessive bradykinin production, which causes increased vascular permeability and angioedema. Factor H, DAF, and CD59 are also complement regulatory proteins, but their deficiencies are associated with different clinical conditions (e.g., Factor H with atypical hemolytic uremic syndrome, DAF/CD59 with paroxysmal nocturnal hemoglobinuria).