Niemann-Pick C disease

Niemann-Pick C (NPC) is a systemic disorder that affects liver, spleen, and lung, but the primary signs and symptoms are attributable to the CNS. Although neonatal cholestatic disease is seen in approximately 50% of diagnosed patients, juvenile onset dystonia, vertical supranuclear gaze palsy, gelastic catatonia, and seizures are the more common manifestations. Because glycosphingolipids such as glucosylceramide, lactosylceramide, GM2, GM3, and asialo-GM2 gangliosides accumulated in brain tissue of patients with NPC, the disorder was first classified as a lysosomal glycosphingolipid disorder, possibly an allelic variant of the sphingomyelin storage disease, Niemann-Pick; but it was later determined that NPC was different from the acid sphingomyelinase deficiencies, Niemann-Pick A and B. There are 2 genes identified with NPC: NPC1 and NPC2. The predominant gene defect found in approximately 95% of patients is in the NPC1 gene. The NPC protein appears to function as a “border patrol” in lysosomes, allowing some lipids to enter and eventually be degraded while diverting others to different regions such as the plasma membrane.

We now know that the disease results primarily from a defect in cholesterol trafficking: defective intracellular …