A lysosomal storage disease due to sphingomyelin accumulation in the reticuloendothelial system; there are five types distinguished by age of onset, amount of central nervous system involvement, and degree of enzyme deficiency. At least some types are characterized by foamy reticular cells containing phospholipids which infiltrate the liver, spleen, lungs, lymph nodes, and bone marrow.Niemann–Pick diseases are a subgroup of lipid storage disorders called sphingolipidoses in which harmful quantities of fatty substances, or lipids, accumulate in the spleen, liver, lungs, bone marrow, and brain. In the classic infantile type-A variant, a missense mutation causes complete deficiency of sphingomyelinase. Sphingomyelin is a component of cell membrane including the organellar membrane, so the enzyme deficiency blocks degradation of lipid, resulting in the accumulation of sphingomyelin within lysosomes in the macrophage-monocyte phagocyte lineage. Affected cells become enlarged, sometimes up to 90 μm in diameter, secondary to the distention of lysosomes with sphingomyelin and cholesterol. Histology shows lipid-laden macrophages in the marrow and "sea-blue histiocytes" on pathology. Numerous small vacuoles of relatively uniform size are created, giving the cytoplasm a foamy appearance.
No specific treatment is known for type A, but symptoms are treated. In adult patients with type B, physicians try to keep cholesterol levels down to normal levels. If statins are used, they monitor liver function. If the spleen is enlarged and platelet levels low, acute episodes of bleeding may require transfusions of blood products. If they have symptoms of interstitial lung disease, they may need oxygen. Anecdotally, organ transplant has been attempted with limited success. Future prospects include enzyme replacement and gene therapy. Bone marrow transplant has been tried for type B.Results of a survey shows the extrapolation of Prevalence Rate of Niemann-Pick disease type C2 in Sweden is 59.Niemann-Pick Type C is a genetic, cholesterol storage disorder that primarily strikes children with death occurring before or during adolescence. There is also an adult onset form of the disease.