Hereditary angioedema

Microbiology

Hereditary angioedema is an autosomal dominant condition associated with low plasma levels of the C1 inhibitor (C1-INH) protein. C1-INH is a multifunctional serine protease inhibitor - the probable mechanism behind attacks is uncontrolled release of bradykinin resulting in oedema of tissues.

Investigation

C1-INH level is low during an attack
low C2 and C4 levels are seen, even between attacks. Serum C4 is the most reliable and widely used screening tool

Symptoms

attacks may be proceeded by painful macular rash
painless, non-pruritic swelling of subcutaneous/submucosal tissues
may affect upper airways, skin or abdominal organs (can occasionally present as abdominal pain due to visceral oedema)
urticaria is not usually a feature

Management

acute: IV C1-inhibitor concentrate, fresh frozen plasma (FFP) if this is not available
prophylaxis: anabolic steroid Danazol may help