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Niemann-Pick disease type C
Also known as Niemann-Pick type C (adult-onset)
NPC leads to the harmful build-up of these substances in various organs, including the brain, liver, and spleen. It can affect individuals from infancy into adulthood, with symptoms varying widely in onset and severity.
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Overview
Niemann-Pick disease type C (NPC) is a lysosomal storage disorder, a group of conditions characterised by the accumulation of various substances within lysosomes, which are the 'recycling centres' of cells. In NPC, the primary issue is the abnormal accumulation of cholesterol and other fatty substances (lipids) inside cells. This build-up particularly affects organs such as the brain, liver, and spleen [PMID:33678000].
The disease is progressive, meaning symptoms tend to worsen over time. The age at which symptoms first appear can vary significantly, ranging from early infancy to late adulthood. This variability makes NPC a challenging condition to diagnose, as its presentation can mimic other neurological or liver disorders. It is classified as an inherited metabolic disorder (IEM) and affects approximately 1 in 120,000 to 150,000 people globally.
The impact of NPC is systemic, affecting multiple body systems. The accumulation of lipids disrupts normal cell function, leading to a range of clinical signs that reflect the specific cells and organs most affected by this storage. Understanding the genetic basis and the cellular processes involved is key to managing this complex condition.
Symptoms & clinical features
The symptoms of Niemann-Pick type C are highly variable, even within the same family, and can change over time. Symptoms are often categorised by the age of onset: early-onset forms (infancy to childhood) typically present with more severe and rapidly progressing signs, while later-onset forms (adolescence to adulthood) may have a slower progression.
Neurological symptoms are a hallmark of NPC and can include problems with balance and coordination (ataxia), difficulty moving the eyes voluntarily (vertical supranuclear gaze palsy), slurred speech (dysarthria), and swallowing difficulties (dysphagia). Cognitive decline, seizures, and psychiatric manifestations such as depression or psychosis can also occur, particularly in adolescent and adult-onset forms [PMID:30612140].
Beyond neurological issues, visceral symptoms (affecting internal organs) are common. An enlarged spleen (splenomegaly) and enlarged liver (hepatomegaly) are often early signs, especially in paediatric cases. Liver dysfunction, including jaundice and prolonged cholestasis in infancy, can also be prominent. In some cases, respiratory issues and lung disease may develop due to lipid accumulation in lung tissues.
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Affected organs
Niemann-Pick type C primarily affects organs where cholesterol and lipid metabolism are most active, or where the accumulation of these substances has the most significant functional impact. The brain and central nervous system are commonly affected, leading to a range of neurological impairments. This includes structures responsible for movement control, such as the cerebellum, as well as areas involved in cognitive function and psychiatric health.
The liver and spleen are also frequently involved, often showing enlargement (hepatosplenomegaly) due to the build-up of cholesterol and glycosphingolipids within their cells. This can lead to impaired liver function, which may manifest as jaundice or other liver-related complications, particularly in younger individuals [PMID:28795537]. Other organs that can be affected include the lungs, potentially leading to respiratory problems, and, less commonly, the kidneys.
Risks & severity
The severity of Niemann-Pick type C varies considerably. Generally, the earlier the onset of symptoms, the more rapidly the disease tends to progress and the more severe the clinical picture. Infantile-onset forms, typically presenting before the age of two, are often the most severe, with rapid neurological decline and significant visceral involvement.
Later-onset forms, appearing in childhood, adolescence, or adulthood, usually progress more slowly. Adult-onset NPC may present predominantly with psychiatric symptoms or subtle neurological signs initially, making diagnosis challenging. The specific symptoms and their progression depend on which organs are most affected and the specific genetic changes present.
Without appropriate management, NPC can lead to significant disability and reduced life expectancy. However, with advances in diagnosis and care, the outlook for individuals with NPC is improving. Early diagnosis is important as it allows for the implementation of supportive care and specific therapies that may help to slow disease progression.
Genetic causes
Niemann-Pick type C is caused by pathogenic variants in one of two genes: NPC1 or NPC2. These genes provide instructions for making proteins that are crucial for the proper movement of cholesterol and other lipids within cells.
About 95% of individuals with NPC have pathogenic variants in the NPC1 gene. The NPC1 protein is primarily located in the membrane of late endosomes and lysosomes, where it functions as a transmembrane protein responsible for moving cholesterol out of these cellular compartments [PMID:33678000]. When the NPC1 protein is faulty, cholesterol cannot be properly transported, leading to its accumulation.
Pathogenic variants in the NPC2 gene account for the remaining 5% of NPC cases. The NPC2 gene codes for a soluble protein that binds to cholesterol within lysosomes. Its proper function ensures cholesterol is transported efficiently out of these cellular compartments. Disruptions in either NPC1 or NPC2 lead to the characteristic build-up of cholesterol and other lipids, causing cellular dysfunction and the symptoms of Niemann-Pick type C.
- NPC1 NPC intracellular cholesterol transporter 1
- NPC2 NPC intracellular cholesterol transporter 2The NPC2 gene provides instructions for a protein critical in regulating cholesterol movement within cells, with specific variants linked to Niemann-Pick disease type C2.
Inheritance pattern
Niemann-Pick type C is inherited in an autosomal recessive pattern. This means that an individual must inherit two copies of a pathogenic variant - one from each parent - to develop the condition.
Parents who each carry one copy of a pathogenic variant (and do not have NPC themselves) are known as carriers. When two carriers have a child, there is a 25% chance with each pregnancy that the child will inherit two pathogenic variants and develop NPC. There is also a 50% chance the child will be a carrier like their parents, and a 25% chance the child will inherit two working copies of the gene and not be affected or a carrier.
Family members of an affected individual, especially siblings, may be offered genetic counselling to discuss carrier testing and reproductive options. This helps families understand the risks and make informed decisions about future pregnancies.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
Subtypes & variants
This page covers Niemann-Pick disease type C as a single condition. Several distinct variants and clinical subtypes are recognised in the literature - they share the underlying biology and broad management approach, but differ in severity, age of onset, or causative gene:
- Adult-onset OMIM 257220
Later-onset NPC presenting in adulthood with psychiatric symptoms (psychosis, depression), cognitive decline, and movement disorders. Vertical supranuclear gaze palsy is a key clinical clue. Slower progression than the infantile or juvenile forms.
Diagnosis & testing
Diagnosing Niemann-Pick type C can be challenging due to its varied symptoms and overlap with other conditions. A suspected diagnosis often begins with clinical assessment based on a combination of neurological and visceral signs, such as unexplained hepatosplenomegaly or progressive neurological decline with impaired eye movements.
Biomarker testing can provide strong evidence for NPC. Tests measuring specific oxysterols (e.g., cholestane-3β, 5α, 6β-triol or 'C-triol') in blood or plasma are increasingly used as a screening tool, as elevated levels are characteristic of NPC [PMID:28795537]. Definitive diagnosis is confirmed through genetic testing, which identifies pathogenic variants in the NPC1 or NPC2 genes. This testing is crucial for confirming the diagnosis, guiding management, and informing family planning.
In the UK, suspected cases of NPC may be referred to clinical genetics services for assessment and genetic testing. This often falls under NHS Genomic Medicine Service pathways, with specific R-codes for inherited metabolic disorders. Genetic counsellors play a vital role in explaining the testing process, results, and implications for the patient and their family.
Management & lifestyle
The management of Niemann-Pick type C aims to alleviate symptoms, slow disease progression, and improve quality of life. Management is typically multidisciplinary, involving specialists such as neurologists, hepatologists, ophthalmologists, and physiotherapists.
One specific medication, miglustat, is approved in the UK for the treatment of progressive neurological symptoms in some individuals with NPC. Miglustat works by reducing the production of certain lipids, which may help to slow the accumulation of these substances in cells. Supportive therapies are also crucial, including physiotherapy, occupational therapy, and speech and language therapy to address neurological symptoms like ataxia, dysphagia, and dysarthria.
Regular monitoring of liver function, neurological status, and other affected organ systems is an important part of ongoing care. Genetic counsellors provide essential support by offering information about the condition, inheritance patterns, and accessing support networks. As research continues, new therapies and clinical trials may become available, offering further options for individuals with NPC.
UK care pathway
In the UK, individuals suspected of having Niemann-Pick type C are typically referred by their GP or a specialist to a regional clinical genetics service or a metabolic specialist centre. These centres are part of the NHS Genomic Medicine Service (GMS) pathways, which provide access to specialist diagnostic testing and care.
Genetic testing for NPC is usually carried out through the GMS using specific R-codes for inherited metabolic disorders. A clinical geneticist or a metabolic consultant will oversee the diagnostic process and help coordinate ongoing management. Genetic counsellors are integral to this pathway, providing comprehensive information, support, and guidance to patients and their families, including discussions around inheritance and family planning.
Access to specialised treatments and multidisciplinary care teams is central to the UK approach, ensuring that individuals with NPC receive tailored support to manage their complex needs and improve their quality of life.
Frequently asked questions
What is the difference between Niemann-Pick type C and other Niemann-Pick types?
Niemann-Pick type C (NPC) is distinct from Niemann-Pick types A and B. NPC involves problems with cholesterol transport within cells, primarily due to mutations in the NPC1 or NPC2 genes. Types A and B are caused by a deficiency of the acid sphingomyelinase enzyme, leading to a build-up of sphingomyelin, and are generally more severe with earlier onset.
How is Niemann-Pick type C inherited?
NPC is inherited in an autosomal recessive pattern. This means a child must inherit two copies of a pathogenic gene variant - one from each parent - to develop the condition. Parents who carry one copy are typically healthy and are known as carriers.
Are there treatments available for Niemann-Pick type C?
Yes, there are treatments available that can help manage the symptoms and potentially slow the progression of Niemann-Pick type C. Miglustat is one medication approved in the UK for neurological symptoms. Supportive therapies, such as physiotherapy and occupational therapy, are also crucial for managing the condition.
What does it mean to be a carrier for Niemann-Pick type C?
Being a carrier for Niemann-Pick type C means you have one pathogenic variant in either the NPC1 or NPC2 gene, but you do not have the condition yourself and usually do not experience symptoms. Carriers can pass the gene variant to their children.
Where can I find support for Niemann-Pick type C in the UK?
In the UK, support for Niemann-Pick type C can be accessed through NHS clinical genetics services and specialist metabolic centres. Patient organisations, such as Niemann-Pick UK, offer valuable resources, information, and a community for affected individuals and families.
References
- Keam SJ. Arimoclomol: First Approval. Drugs. 2025. PMID: 39715913
- Chu TT, Tu X, Yang K. Tonic prime-boost of STING signalling mediates Niemann-Pick disease type C. Nature. 2021. PMID: 34290407
- Adam MP, Bick S, Mirzaa GM. Niemann-Pick Disease Type C. 1993. PMID: 20301473
- Wraith JE. Lysosomal disorders. Seminars in neonatology : SN. 2002. PMID: 12069540
- Bremova-Ertl T, Claassen J, Foltan T. Efficacy and safety of N-acetyl-L-leucine in Niemann-Pick disease type C. Journal of neurology. 2022. PMID: 34387740
- Vanier MT, Millat G. Niemann-Pick disease type C. Clinical genetics. 2003. PMID: 12974729
- Mengel E, Patterson MC, Da Riol RM. Efficacy and safety of arimoclomol in Niemann-Pick disease type C: Results from a double-blind, randomised, placebo-controlled, multinational phase 2/3 trial of a novel treatment. Journal of inherited metabolic disease. 2021. PMID: 34418116
- Roney JC, Li S, Farfel-Becker T. Lipid-mediated motor-adaptor sequestration impairs axonal lysosome delivery leading to autophagic stress and dystrophy in Niemann-Pick type C. Developmental cell. 2021. PMID: 33878344