Health condition
Selective IgA deficiency deep dive
Selective IgA deficiency - absent IgA with normal IgG and IgM - is the commonest primary immunodeficiency, affecting roughly 1 in 600 people; most are healthy, but a minority have recurrent infections, autoimmunity or coeliac disease, and a few evolve towards CVID.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Most people with absent IgA are entirely well and need no treatment - it is often found incidentally
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The symptomatic minority get recurrent sinus, ear and chest infections and gut infections such as giardia
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Associations worth knowing: coeliac disease (and IgA-based coeliac tests will be falsely negative - the lab must use IgG-based tests), autoimmune conditions, and atopy
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A small proportion progress to broader antibody failure - new or worsening infections warrant re-checking IgG and vaccine responses
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Rare but important: anti-IgA antibodies can cause transfusion reactions - carry the information and tell clinicians before blood products
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
IgA is the antibody of surfaces - saliva, tears, gut and airway linings - and its absence is usually compensated by IgM stepping into secretions. That is why most affected people never know. Where problems occur they concentrate at those surfaces: recurring sinusitis and bronchitis, prolonged gut infections, and an odd but well-documented tilt toward autoimmunity and coeliac disease. The laboratory trap matters to thousands: standard coeliac screening measures IgA-class antibodies, which an IgA-deficient person cannot make, so their coeliac disease goes unfound unless total IgA is checked alongside.
Diagnosis and treatment routes
Assessment separates the well (documentation, coeliac awareness, transfusion advice, no follow-up needed) from the symptomatic, who deserve fuller testing: IgG subclasses, vaccine-response testing, and monitoring for evolution toward CVID, since IgA deficiency and CVID sit on a spectrum in some families. Treatment for the symptomatic is targeted - prompt antibiotics, sometimes prophylactic courses through winter - as immunoglobulin replacement is rarely appropriate. If you keep getting surface infections and your IgA is absent, an immunology review is worthwhile; privately, typically within about two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant clinical immunologist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Selective IgA deficiency deep dive.
Quick, plain-English answers to what people ask us most.
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What is selective IgA deficiency?
Selective IgA deficiency - absent IgA with normal IgG and IgM - is the commonest primary immunodeficiency, affecting roughly 1 in 600 people; most are entirely well, but a minority have increased infections or associated autoimmune conditions.
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What causes selective IgA deficiency?
It results from a specific defect in the development of IgA-producing immune cells, though the exact cause of this defect in most individuals isn't fully understood, and it can occasionally run in families.
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Is selective IgA deficiency dangerous?
Most people with selective IgA deficiency are asymptomatic and lead entirely normal lives, though a minority experience recurrent sinus or respiratory infections, and there is a recognised association with certain autoimmune conditions.
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Why does selective IgA deficiency matter for blood transfusions?
People with selective IgA deficiency can, rarely, have a severe allergic-type reaction to blood products containing IgA, so it's important that this is documented and specific transfusion precautions are taken if you ever need blood products.
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How is selective IgA deficiency diagnosed?
Diagnosis is made through blood tests showing absent or very low IgA with normal levels of other immunoglobulins (IgG and IgM).
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How is selective IgA deficiency managed?
Most people need no specific treatment beyond awareness of the diagnosis for future transfusion safety, though those with recurrent infections may need closer monitoring or additional preventive measures.
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When should I see a specialist about selective IgA deficiency?
See a doctor if you have recurrent infections or a known IgA deficiency needing further characterisation. A private clinical immunologist can typically be seen within about two weeks.