Health condition
Secondary immunodeficiency causes
Most immunodeficiency in adults is secondary - caused by medications, blood cancers, protein loss or chronic disease rather than genetics - and recognising the cause matters because many forms are reversible or specifically treatable.
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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Leading culprits: medications (rituximab, long-term steroids, immunosuppressants, some anti-epileptics), haematological cancers (CLL, myeloma, lymphoma), and protein loss through kidneys or gut
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The screening question in recurrent infection is always double-barrelled: is the immune system failing, and if so, why now?
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Basic screen: full blood count, immunoglobulins with serum electrophoresis (myeloma can masquerade as low antibodies), HIV test, urine protein, and medication review
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Management targets the cause where possible; immunoglobulin replacement is used for significant antibody failure with infections - common in CLL and after rituximab
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New-onset low immunoglobulins in an adult always warrant haematological thought - secondary causes outnumber late-presenting primary ones
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
The adult immune system rarely fails without a reason, and the reasons follow patterns: rituximab deletes B cells and can leave immunoglobulins low for years afterwards; chronic lymphocytic leukaemia erodes antibody production so gradually that recurrent chest infections precede the diagnosis; myeloma crowds out normal immunoglobulins while producing its useless paraprotein; nephrotic syndrome and protein-losing gut disease simply pour antibodies away. Add long-term steroids, biologics, poorly controlled diabetes and alcohol, and the differential for 'too many infections' becomes mostly a medication list and a set of routine bloods.
Diagnosis and treatment routes
The assessment is systematic rather than exotic - history and drug chart, immunoglobulins with electrophoresis and free light chains, HIV serology, urinalysis, and targeted haematology referral when the pattern points there - and treatment follows cause: adjusting or spacing drugs, treating the underlying cancer, vaccinating strategically, prophylactic antibiotics, and immunoglobulin replacement where antibody failure and infections coexist. Recurrent significant infections in adulthood always deserve this screen; a private immunology review is typically available within about two weeks, against NHS waits often of several months.
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 Secondary immunodeficiency causes.
Quick, plain-English answers to what people ask us most.
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What causes secondary immunodeficiency?
Most immunodeficiency in adults is secondary - caused by medications, blood cancers, protein loss (such as through the kidneys or gut) or chronic disease rather than genetics - and recognising this pattern guides appropriate treatment.
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How does secondary immunodeficiency differ from primary immunodeficiency?
Primary immunodeficiency is present from birth due to a genetic cause, whereas secondary immunodeficiency develops later in life due to an external cause such as medication, illness, or protein loss affecting immune function.
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What are the symptoms of secondary immunodeficiency?
Symptoms include increased frequency, severity or duration of infections, similar to primary immunodeficiency, but occurring in the context of an underlying cause such as chemotherapy, certain medications, or chronic illness.
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Is secondary immunodeficiency reversible?
Sometimes - if the underlying cause can be treated or medication adjusted, immune function may improve, though some causes lead to more persistent immune impairment needing ongoing management.
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How is secondary immunodeficiency treated?
Treatment addresses the underlying cause where possible, alongside supportive measures such as vaccinations, prompt treatment of infections, and in some cases immunoglobulin replacement therapy.
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How is secondary immunodeficiency investigated?
Investigation includes blood tests to assess immune function and antibody levels, alongside a careful review of medications and any underlying conditions that could be contributing.
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When should I see a specialist about secondary immunodeficiency?
See a doctor if you're experiencing recurrent or unusual infections, particularly alongside a relevant medication or health condition. A private consultant clinical immunologist can typically be seen within about two weeks.