Health condition
Rituximab hypogammaglobulinaemia
Rituximab and other B-cell-depleting therapies can leave immunoglobulin levels low for months or years after treatment - usually harmlessly, but in a minority causing recurrent infections that respond to immunoglobulin replacement.
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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Rituximab deletes CD20 B cells; repeated courses, prior chemotherapy, and low baseline IgG raise the risk of prolonged hypogammaglobulinaemia
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Best practice is baseline immunoglobulins BEFORE starting B-cell depletion, then periodic monitoring during and after - a step still often missed
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Low IgG alone is not an indication to treat: the combination with recurrent or severe bacterial infections is what matters
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Vaccine responses are blunted during depletion - vaccinate before treatment where possible, and time doses sensibly around cycles
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Persistent symptomatic cases merit immunology referral for vaccine-response testing and consideration of immunoglobulin replacement
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
B-cell depletion has transformed lymphoma, rheumatoid arthritis, vasculitis and MS care, and most patients regenerate B cells within a year without incident - existing long-lived plasma cells keep making antibody meanwhile. But a significant minority, especially after multiple courses or with unrecognised low immunoglobulins at the start, drift into sustained hypogammaglobulinaemia; some of these had a quiet primary antibody deficiency all along, unmasked when treatment removed the compensation. Their sinus and chest infections begin months after the infusions, when no one connects the two.
Diagnosis and treatment routes
The safeguards are mostly scheduling: immunoglobulins checked at baseline (with a pause for thought if already low), monitored six-to-twelve-monthly during maintenance and after stopping, infections documented, and referral triggered by the combination of low IgG and clinical trouble - where immunology can test vaccine responses and, when criteria are met, start replacement therapy that usually works well. If you have had rituximab and infections keep recurring, ask when your immunoglobulins were last measured; a private immunologist can typically assess you 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 Rituximab hypogammaglobulinaemia.
Quick, plain-English answers to what people ask us most.
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What is rituximab-associated hypogammaglobulinaemia?
Rituximab and other B-cell-depleting therapies can leave immunoglobulin levels low for months or years after treatment - usually harmlessly, but in a minority of patients this leads to increased susceptibility to infection needing active management.
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What causes low immunoglobulins after rituximab?
Rituximab works by depleting the B-cells that produce antibodies, and while B-cell numbers usually recover within months, antibody (immunoglobulin) production can remain low for a much longer period in some people.
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Is low immunoglobulin after rituximab dangerous?
For most people it causes no problems, but in a minority it increases susceptibility to infections, particularly recurrent chest or sinus infections, which is why monitoring immunoglobulin levels and infection frequency is recommended.
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How is hypogammaglobulinaemia after rituximab monitored?
Monitoring involves periodic blood tests to check immunoglobulin levels, alongside tracking how often and how severely infections occur, particularly in the months following treatment.
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How is hypogammaglobulinaemia after rituximab treated?
For those with significant low levels and recurrent infections, immunoglobulin replacement therapy can be given to restore adequate antibody levels and reduce infection frequency.
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How long do immunoglobulin levels stay low after rituximab?
This varies considerably between individuals - some recover within months, while others have persistently low levels for years, particularly after repeated courses of treatment.
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When should I see an immunologist about low immunoglobulins after rituximab?
See a doctor if you notice increased frequency or severity of infections after rituximab treatment, so immunoglobulin levels can be checked. A private consultant clinical immunologist can typically be seen within about two weeks.