C1 Esterase Inhibitor (C1-INH) deficiency is associated with Hereditary Angioedema (HAE) and Acquired Angioedema.
Hereditary Angioedema (HAE)
HAE Clinical Features
- 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 (autosomal dominant inheritance), episode of laryngeal oedema, recurrent episodes of unexplained abdominal pain and vomiting.
- Steroids and antihistamines are not effective in attacks.
- Consider if angioedema episodes are drug induced (ACEI); allergic; acquired; idiopathic.
HAE Investigation
This involvesmeasuring blood Complement C3 & 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 C1 inhibitor concentrate / bradykinin receptor antagonists for treating future episodes and should be referred. Acute treatment with plasma derived C1-inhibitor concentrate or recombinant C1 inhibitor shortens attacks.
Complement C3 and C4 level measurement can be used to monitor disease activity in
SLE. Levels fall with disease activity due to complement consumption.
C.M. & C.C. 22-0-25
Who to refer:
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 – please see Immunology for full contact details.
