Niemann-Pick Type C (NPC) disease is a genetic, neurodegenerative disorder which causes progressive deterioration of the nervous system.
It usually affects children by interfering with their ability to metabolize cholesterol. Adult onset may also occur. Large amounts of cholesterol accumulate within the liver, spleen, and brain. This metabolic disorder leads to a series of neurological problems that are ultimately fatal…until a treatment is found.
Learn more about the Niemann Pick Type C from the Parseghian family and other families on our YouTube page.
In 1997 medical researchers funded by the Parseghian Foundation identified the location of a gene called NPC1 that is abnormal in patients with Niemann-Pick Type C disease. The NPC1 gene is on chromosome 18 and is normally present in two copies in each cell of the body. However, alterations or mutations in this gene cause about 95 percent of cases of NPC disease.
In a second smaller group of patients with NPC, alternations in NPC1 do not cause the disease. Researchers suspect a second gene, called NPC2, may be responsible.
The proteins encoded by these genes are involved in the trafficking of lipids and other large molecules within cells. More than 400 mutations have been identified in NPC1 (Shammas 2019) and more than 20 have been identified in NPC2 (Zampieri 2014). The mutations result in intracellular accumulation of complex lipid compounds, causing an inflammatory response and increased cell death in multiple organs and tissues across the lifespan. The disease can present at any stage of life and can strike unexpectedly with highly variable and insidious symptomatology.
Niemann-Pick Type C disease is known as an autosomal recessive inherited condition. This means that each parent of an affected child has one functional NPC1 gene, plus one non-functional NPC1 (or more rarely, NPC2) gene. These parents are called carriers, or heterozygotes, and exhibit no signs or symptoms of the disease. Affected children inherit two non-functional NP-C genes from their parents.
In each pregnancy of a carrier couple, there is a one in four (25 percent) chance that they will both pass their non-functional NPC genes to a child who would then be affected. There is a one in two (50 percent) chance that only one of them would pass a non-functional gene. The child would then be a carrier like the parents. There is a 25 percent chance that both functional genes would be passed and the child would be neither a carrier nor affected with the disease.