C1 inhibitor deficiency

= autosomal dominant disease resulting in inherited or acquired deficiency in C1 inhibitor

– symptoms generally start in late teenage years and present as recurrent episodes of angioedema without urticaria and abdominal pain (due to mesenteric oedema)

– symptoms are made worse or can be triggered by oestrogens (progesterone-only pill should be recommended instead of the combined pill)

Investigations:

– C4 done level during the episode of angioedema: a level of 100% rules out C1 inhibitor deficiency, while a C4 level of less than 50% is diagnostic of C1 inhibitor deficiency

Management:

– airway management is most important

– C1 inhibitor should be administered immediately (if available – some patients carry their own) when there is any suspicion of airway involvement; it is sometimes used for severe abdominal pain as well. C1 inhibitor is a human plasma-derived product.

– adrenaline / antihistamines / steroids are of no benefit

– FFP has been used in the past, but it can worsen the symptoms initially

– tranexamic acid is recommended to prevent recurrence of attacks, but its role in the acute management is not clear