16th February 2025

An 18-year-old male is referred to the allergy clinic by the general practitioner with a four-month history of recurrent episodes of facial swelling, particularly affecting his lips and eyelids.

An 18-year-old male is referred to the allergy clinic by the general practitioner with a four-month history of recurrent episodes of facial swelling, particularly affecting his lips and eyelids. There is no associated pruritus or erythema. He believes the latest episode was triggered by minor trauma to the face.

His father has had similar episodes since a young age and also suffers from rheumatoid arthritis.

Routine skin prick testing is negative, and complement studies show the following:

C1-inhibitor level: normal

C1-inhibitor function: low

C1q level: normal

Which of the following is the most likely diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.