has part has core process sphingomyelinase gene mutation [Niemann Pick Disease Type A/ B] course of Niemann–Pick disease type A and type B Niemann–Pick disease type A and type B are inherited as autosomal recessive deficiency of the enzyme sphingomyelinase, in the lysosomes of the reticuloendothelial system. This results in the lysosomal storage of sphingomyelin. The liver and spleen are predominantly involved. Sherlock's Diseases of the Liver and Biliary System, 12th Edition PMID:20111001 The totality of all processes through which the Niemann–Pick disease type A or type B is realized. This causal process is heredity. https://ghr.nlm.nih.gov/condition/niemann-pick-disease dysfunction of sphingomyelin degradation [Niemann Pick Disease Type A/ B] sphingomyelin metabolism imbalance [Niemann Pick Disease Type A/ B] pulmonary infection [Niemann Pick Disease Type A/ B] sphingomyelin disorder (genetic) severe sphingomyelin accumulation in lysosome [Niemann Pick Disease Type A/ B (severe)] liver malfunction [Niemann Pick Disease Type A/ B] spleen malfunction [Niemann Pick Disease Type A/ B] increasing number of macrophage derived foam cell (niemann pick cell) [Niemann Pick Disease Type A/ B] Niemann–Pick disease course sphingomyelin homeostasis imbalance [Niemann Pick Disease Type A/ B] hepatic fibrosis [Niemann-Pick disease] hypofunction of cholesterol efflux [Niemann-pick disease]