Niemann-Pick Disease Overview – Types A, B and C
Niemann-Pick Disease is one of a group of lysosomal storage diseases that affect metabolism and that are caused by genetic mutations. The three most commonly recognized forms are Niemann-Pick Types A and B (ASMD or Acid Sphingomyelinase Deficiency) and Niemann-Pick Disease Type C (NPC).
The National Niemann-Pick Disease Foundation (NNPDF) supports and promotes research to find treatments and a cure for all types of Niemann-Pick Disease, and provides support services for individuals and families affected by NPD. Our Vision is a world where Niemann-Pick Disease is no longer a threat to a full and productive life for patients and their families.
Membership in the NNPDF is free and helps ensure we can keep families affected by Niemann-Pick Disease up to date with all the latest news and research information. Please contact the NNPDF for a membership form or download the PDF here.
Niemann-Pick Disease affects all segments of the population with cases reported in North America, South America, Europe, Africa, Asia, and Australia. However, a higher incidence of NPD has been found in certain populations:
- Ashkenazi Jewish population (NPA and NPB)
- French Canadian population of Nova Scotia (Type D, now considered a variant of Type C or NPC)
- Maghreb region (Tunisia, Morocco, and Algeria) of North Africa (NPB)
- Spanish-American population of southern New Mexico and Colorado (NPC)
Please continue reading below for more information about each type of Niemann-Pick Disease (NPD). We invite you to contact the NNPDF if you would like further information or if you have any questions about NPD. We are here to provide information, support and referrals and to advance essential research into effective treatments and a cure.
Niemann-Pick Disease Types A (NPA) and B (NPB), also known as ASMD or
Acid Sphingomyelinase Deficiency
Niemann-Pick Types A and B (NPA and NPB), also called Acid Sphingomyelinase Deficiency (ASMD), are caused by the deficiency of a specific enzyme, acid sphingomyelinase (ASM). This enzyme is found in special compartments within cells called lysosomes and is required to metabolize a lipid called sphingomyelin (by tradece potter). If ASM is absent or not functioning properly, sphingomyelin cannot be metabolized properly and is accumulated within the cell, eventually causing cell death and the malfunction of major organ systems.
NPA and NPB are both caused by the same enzymatic deficiency and there is growing evidence that the two forms represent opposite ends of a continuum. People with NPA generally have little or no ASM production (less than 1% of normal) while those with NPB have approximately 10% of the normal level of ASM.
Forms of ASMD between these two extremes do occur, and the diagnosis is sometimes called intermediate NPD or Type A/B. There can be considerable overlap along the entire ASMD disease spectrum with symptoms ranging in onset, complexity and severity, and every patient’s case is unique.
The clinical prognosis for NPA and NPB patients is very different. NPA is a severe neurologic disease that leads to an early death, usually by 2 to 4 years of age. In contrast, patients with NPB generally have little or no neurologic involvement and may survive into adulthood, though there may be health complications. Type B individuals usually have enlarged livers and spleens, and respiratory problems are common. The enlargement of organs and the respiratory problems can cause cardiovascular stress and can lead to heart disease.
There are approximately 1,200 cases of NPA and NPB worldwide with the majority being Type B or an intermediate form.
- Diagnosing Niemann-Pick Disease Type A (NPA), also known as ASMD or Acid Sphingomyelinase Deficiency
- Diagnosing Niemann-Pick Disease Type B (NPB), also known as ASMD or Acid Sphingomyelinase Deficiency
Mia’s NPA Timeline — blog chronicling one family’s journey through Niemann-Pick Disease Type A
NNPDF’s brochure on ASMD (pdf)
Niemann-Pick Disease Type C (NPC)
Niemann-Pick Type C (NPC) is very different than Type A or B (ASMD). NPC Patients are not able to metabolize cholesterol and other lipids properly within the cell. Consequently, excessive amounts of cholesterol accumulate within the liver and spleen and excessive amounts of other lipids accumulate in the brain. NPC causes a secondary reduction of ASM activity, which led all three types to be considered forms of the same disease.
There is considerable variation in when Type C symptoms first appear and in the progression of the disease. Symptoms may appear as early as a few months of age or as late as adulthood.
Vertical gaze palsy (the inability to move the eyes up and down), enlarged liver, enlarged spleen, or jaundice in young children are strong indications that NPC should be considered. It is common for only one or two symptoms to appear in the early stages of the disease.
In most cases, neurological symptoms begin appearing between the ages of 4 and 10. Generally, the later neurological symptoms begin, the slower the progression of the disease.
Type C Niemann-Pick Disease has an estimated 500 cases diagnosed worldwide. It is believed, however, that the number of people affected by NPC is higher, but diagnostic difficulties do not allow an accurate assessment of the occurrence rate. NPC has been initially diagnosed as a learning disability, mild retardation, “clumsiness,” and delayed development of fine motor skills. It is not uncommon for a family to spend several years seeking a diagnosis before NPC is identified.
NPC is always fatal. The majority of children with NPC die before age 20 (many die before the age of 10). Late onset of symptoms can lead to longer life spans but it is extremely rare for any person with NPC to reach age 40.
National Institute of Child Health and Human Development at the National Institutes of Health (NIH) (once on the NICHD site, search “niemann-pick” without the quotation marks for links to articles, etc.)
The Progression of Niemann-Pick Disease — NNPDF parents tell their families’ stories in words and photographs
NNPDF’s brochure on NPC (pdf)
- Links and other NPD Resources
- The Mount Sinai International Center for Types A and B Niemann-Pick Disease
- National Institute of Child Health and Human Development at the National Institutes of Health (NIH)
- Other NPD organizations
- Organizations addressing other lysosomal storage diseases
Pick’s Disease is sometimes confused with Niemann-Pick Disease but it is a different disease. The NNPDF works exclusively with Niemann-Pick Disease, not Pick’s Disease. Here are a few resources on Pick’s Disease, posted as a courtesy.