A group of inherited, severe metabolic disorders in which sphingomyelin accumulates in lysosomes in cells. The lysosomes normally transport material through and out of the cell. The disease is MONDO_0001982 (Niemann-Pick disease). Also known as: Niemann-Pick disease with cholesterol esterification block, Niemann-Pick disease, subacute juvenile form, lipoid histiocytosis, lipoid histiocytosis (classical phosphatide), sphingomyelin lipidosis, sphingomyelin/cholesterol lipidosis, sphingomyelinase deficiency disease.