Home A-Z conditions C1 Esterase Inhibitor Deficiency
Also known as: C1 Inhibitor Deficiency; Hereditary Angioedema; Hereditary Angioneurotic Oedema
C1 inhibitor deficiency results from a genetic change to the C1 inhibitor gene on chromosome 11. C1 inhibitor deficiency attacks can often be mistaken for anaphylaxis, but adrenaline, antihistamines and steroids (treatments given during anaphylaxis) are ineffective.
People with C1 inhibitor deficiency experience intermittent angioedema (swellings), which last several days if untreated affecting: hands, feet, limbs or face.
Symptoms usually occur infrequently until adolescence when swellings may become more common. Occasionally C1 inhibitor deficiency is asymptomatic (without symptoms).
A genetic mutation of the C1 inhibitor gene causes reduced production of C1 Inhibitor. C1 inhibitor regulates fluid leakage from blood vessels and prevents excess oedema (fluid build up). Low levels of C1 inhibitor result in a tendency for oedema to occur.
C1 inhibitor deficiency is diagnosed when there are typical features of angioedema but without urticaria being present. A diagnosis may be made if: a family member has C1 inhibitor deficiency in many cases
Other causes of angioedema (swellings) include allergies, medications (particularly ACE inhibitors such as lisinopril, often used for high blood pressure) or may be idiopathic (with no known cause).
Given when attacks are frequent to reduce the number and severity of swellings: may include:
Treatment of swellings may be by:
With appropriate treatment, available in specialist centres, people with C1 inhibitor deficiency have normal life expectancy and enjoy good health.
Inheritance patternsC1 inhibitor deficiency is an autosomal dominant genetic condition.
Prenatal diagnosisNot routinely available. However, preimplantation genetic diagnosis to ensure an unaffected baby is sometimes possible, although NHS funding for this is variable.
There is no support group for C1 inhibitor deficiency syndrome in the UK.
If your child is affected by a medical condition or disability, we can help. Call our freephone helpline on 0808 808 3555 to get information, support and advice. We also offer emotional support for parents via our Listening Ear service.
We have a range of parent guides on aspects of caring for a disabled child in our resource library. You may also find our Early Years Support useful, which contains links to parent carer workshops and help for families going through the diagnosis process.
You can also meet other parents online in our closed Facebook group.
Medical text written September 2001 by Dr HJ Longhurst. Last updated December 2012 by Dr HJ Longhurst, Consultant Immunologist, Barts Health NHS Trust, London, UK.
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