The animated videos in NORD’s Rare Disease Video Library provide brief introductions to rare disease topics for patients, caregivers, students, professionals and the public. NORD collaborates with medical experts, patient organizations, videographers and Osmosis to develop the videos, which are made possible by individual donations, educational grants and corporate sponsorships. NORD is solely responsible for the content.
Niemann-Pick disease type C (NPC) is a rare progressive genetic disorder characterized by an inability of the body to transport cholesterol and other fatty substances (lipids) inside of cells. This leads to the abnormal accumulation of these substances within various tissues of the body, including brain tissue. The accumulation of these substances damages the affected areas. NPC is highly variable and the age of onset and specific symptoms can vary from one person to another, sometimes even among members of the same family. NPC can range from a fatal disorder within the first few months after birth (neonatal period) to a late onset, chronic progressive disorder that remains undiagnosed well into adulthood. Most cases are detected during childhood and progress to cause life-threatening complications by the second or third decade of life. NPC is caused by mutations in the NPC1 gene (NPC type 1C) or the NPC2 gene (NPC type 2C) and is inherited in an autosomal recessive manner.
NPC belongs to a larger group of more than 50 disorders known as lysosomal storage disorders. Lysosomes are membrane-bound compartments within cells. They contain enzymes that break down large molecules such as proteins, carbohydrates and fats into their building blocks. Abnormal functioning of a transport protein leads to the accumulation of cholesterol and other fatty substances in various tissues of the body, including brain tissue. NPC used to be grouped together with two other disorders, named Niemann-Pick disease type A and Niemann-Pick disease type B. However, researchers have determined that the underlying defect in types A and B involves mutations in the SMPD1 gene and deficiency of the enzyme acid sphingomyelinase, which does not occur in NPC. Niemann-Pick disease types A and B are now considered a distinct disorder called acid sphingomyelinase deficiency. NORD has a separate report in the Rare Disease Database on this disorder. Niemann-Pick disease type D is an obsolete term for a condition in a group of individuals in Nova Scotia, Canada who have NPC due to a specific founder mutation of the NPC1 gene. This form is clinically indistinguishable from NPC. Additional terms have been used in the past to describe NPC including DAF (down gaze palsy, ataxia, foam cells) syndrome, juvenile dystonic lipidosis, lipid histiocytosis, and sea blue histiocyte disease. These terms are now considered obsolete.