C1 Esterase
Inhibitor (C1-INH) deficiency
is associated with Hereditary Angioedema (HAE) and Acquired Angioedema.
Hereditary Angioedema (HAE)
- Usually starts in childhood (classically, symptoms start at or around puberty)
- Recurrent episodes of angioedema and/or abdominal pain
- Urticaria is NOT usually associated with C1 inhibitor deficiency
- May involve the larynx therefore can be fatal
- Diagnosis is suggested by recurrent episodes of non-urticarial swelling unresponsive to antihistamines, positive family history, episode of laryngeal oedema, recurrent episodes of unexplained abdominal pain and vomiting
- Steroids and anti-histamines are not effective in attacks
- Also consider if angioedema episodes are; drug induced (ACEI), allergic, acquired, idiopathic
- Investigation involves measuring C4 levels, C1- inhibitor levels and C1 inhibitor functional analysis. Complement consumption in vitro can lead to artefactually ‘low’ complement / complement functional levels. Ideally serum samples should reach the laboratory within 4 hours of the sample being taken. Phoning the Immunology laboratory to alert reception
is helpful, so that samples can be looked out for and processed appropriately. - Results of C1 inhibitor level / functional activity dictate subtype- HAE type I, II, or III
If hereditary angioedema (HAE) is diagnosed,
patients may need blood products for future episodes. Plasma derived
C1-inhibitor concentrate shortens attacks , and newer therapies that target the
bradykinin pathway (e.g Icatibant) have also been shown to be effective in treating
acute angioedema episodes in C1 inhibitor deficiency. Patients with HAE/ C1
inhibitor deficiency should be managed with specialist Immunologist input.
Please refer any patients with confirmed / suspected C1 inhibitor Deficiency to
the Clinical Immunology Primary Immune Deficiency Service based at the Royal
Infirmary of Edinburgh.
Complement C3 and C4 can be used to monitor disease activity in
SLE. Levels fall with disease activity due to complement consumption.
