Health condition
Niemann-Pick disease types A and B
Niemann-Pick types A and B (acid sphingomyelinase deficiency, ASMD) are rare inherited storage disorders; type B can present in adulthood with an enlarged spleen and lung involvement, and a licensed enzyme therapy now exists.
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.
Which gene and test confirm it, who should be tested in the family, and which specialist to see.
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Caused by SMPD1 variants; autosomal recessive - now grouped as acid sphingomyelinase deficiency (ASMD)
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Type B (chronic visceral ASMD) presents with splenomegaly, low platelets, abnormal lipids and interstitial lung changes
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Diagnosis: enzyme activity on a blood spot plus SMPD1 genetic testing
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Enzyme replacement therapy (olipudase alfa) is the first disease-modifying treatment
Understanding the condition
What it is and what happens next.
What causes it, how it is confirmed, and the testing and specialist routes available in the UK.
What it is and how it presents
ASMD spans a spectrum: type A is a severe infantile neurological disease, while type B, the form relevant to adults, spares the brain and instead fills the spleen, liver and lungs with storage cells. Adults are often investigated for years for an unexplained large spleen, low platelets, a strikingly low HDL cholesterol or interstitial changes on a chest CT before anyone requests the enzyme test.
Testing, surveillance and specialist care
Diagnosis follows the familiar lysosomal pathway - blood-spot enzyme assay, then SMPD1 sequencing - and management sits with specialist metabolic centres, particularly now that enzyme replacement can reduce spleen size and improve lung function. Family testing and genetic counselling follow a confirmed result. NHS clinical genetics services carry some of the longest waits in the health service, often many months for a first appointment, whereas private genetic testing and a specialist review can typically be arranged within around two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a metabolic physician (inherited metabolic disease clinic). 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 emergency symptoms.
Frequently asked
Common questions about Niemann-Pick disease types A and B.
Quick, plain-English answers to what people ask us most.
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What are Niemann-Pick disease types A and B?
Niemann-Pick disease types A and B are rare inherited metabolic disorders in which a fatty substance called sphingomyelin builds up in cells due to a missing or deficient enzyme, affecting the liver, spleen, lungs and, in type A, the brain.
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What causes Niemann-Pick disease types A and B?
Both are caused by mutations in the SMPD1 gene, leading to deficiency of an enzyme called acid sphingomyelinase, inherited in an autosomal recessive pattern.
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What are the symptoms of Niemann-Pick disease types A and B?
Type A causes severe symptoms in infancy including an enlarged liver and spleen, feeding difficulties and rapid neurological decline, while type B typically has milder, later-onset symptoms mainly affecting the liver, spleen and lungs, without significant neurological involvement.
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Is Niemann-Pick disease hereditary?
Yes, both types are inherited in an autosomal recessive pattern, meaning both parents carry one copy of the faulty gene without necessarily having the condition themselves.
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Is Niemann-Pick disease dangerous?
Type A is a severe, life-limiting condition with significant neurological decline in infancy, while type B varies from mild to more significant organ involvement but generally allows survival into adulthood.
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Can Niemann-Pick disease types A and B be treated?
An enzyme replacement therapy is now available for type B, which can improve organ-related symptoms, though it doesn't cross into the brain and so isn't effective for the neurological features of type A; management otherwise remains largely supportive.
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When should I see a specialist about suspected Niemann-Pick disease, and how quickly can I be seen privately?
See a metabolic specialist for unexplained enlarged liver and spleen, particularly with a relevant family history. A private metabolic specialist can typically arrange assessment within about two weeks.