Niemann-Pick Disease is one of a group of lysosomal storage diseases that affect metabolism and that are caused by genetic mutations. The three most commonly recognized forms are Niemann-Pick Types A and B (ASMD or Acid Sphingomyelinase Deficiency) and Niemann-Pick Disease Type C (NPC).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.
Some forms of the disease can be diagnosed during ante natal screening. After birth, the diagnosis is made by a liver biopsy where liver tissue specimens are obtained and studied under a microscope. Niemann-Pick disease does not have a complete cure, though treatments that halt the disease progression are being studied. Affected children tend to die of infection or progressive dysfunction of the central nervous system.With over 6.5 Billion people in the world now, that 1:150,000 estimate seems to be more like 1 in 2 or 3 Million that have the disease. Either way, it is extremely rare to say the least.There is current research aiming to develop recombinant human acid sphingomyelinase for the potential treatment of NP disease types A and B. A phase 1 clinical trial was completed in 2009. A phase 2 trial is planned.