Niemann-Pick Disease Type C
What is Niemann-Pick Disease Type C?
Niemann-Pick Disease Type C (NPC) is an inherited disorder of cellular cholesterol metabolism characterized by neurologic problems typically presenting in mid to late childhood. Some children present earlier, with problems including liver dysfunction, and onset can be in adulthood also. Affected individuals are unable to normally process cholesterol and other fats in cells of the body, which cause accumulation of these substances in the liver, spleen, and brain.
Key symptoms of NPC include:
- Liver disease
- Lung disease
- Low muscle tone
- Developmental delay
- Vertical supranuclear gaze palsy
- Dystonia (movement disorder)
How many people have Niemann-Pick Disease Type C?
NPC occurs in approximately 1 in 150,000 children. NPC maybe be seen more frequently in individuals of Hispanic descent in parts of Colorado and New Mexico, Acadians in Nova Scotia, and Bedouins in Israel.
What causes Niemann-Pick Disease Type C?
NPC is caused by a mutation or change in the NPC1 or NPC2 genes. Mutations in NPC1 are found in approximately 95% of patients with NPC, while mutations in NPC2 are seen in another 5%. NPC1 and NPC2 genes produce proteins in our cells that help process and transport cholestanol. Therefore, mutations or changes in either the NPC1 or NPC2 gene produce lead to accumulation of cholesterol and lipids in cells. This accumulation keeps cells from functioning normally and eventually leads to cell death.
NPC is an inherited autosomal recessive disorder. Affected individual inherits two copies of the defective gene (either NPC1 or NPC2), one from each parent. Therefore the parents are "carriers" of NPC, meaning that they have one normal functioning copy and one nonfunctioning copy of the gene. With each pregnancy, carriers of NPC have a 1 in 4 or 25% chance of having a child with NPC.
How is Niemann-Pick Disease Type C diagnosed?
NPC is diagnosed by evaluation of the ability of cultured cells to process cholesterol. Genetic testing is also available to detect mutations in the NPC1 or NPC2 genes and is replacing measurement of cholesterol processing as the diagnostic test of choice.
What is/is there treatment for Niemann-Pick Disease Type C?
There is no curative therapy for NPC. Treatment for features of NPC, including seizures, is symptomatic.