High Quality Content by WIKIPEDIA articles! Niemann?Pick disease (pronounced n??mahn pik) refers to a group of fatal inherited metabolic disorders that are included in the larger family of lysosomal storage diseases (LSDs).Niemann-Pick diseases are genetic diseases primarily afflicting Ashkenazi Jews, which are classified in a subgroup of LSDs called sphingolipidoses or lipid storage disorders 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.