Niemann-Pick disease (NP) disease is a rare autosomal recessive lysosomal disease; it involves the accumulation of sphingolipids in cells throughout the body. NP disease is divided into four types based on the genetic cause and the signs and symptoms: type A, type B, type C1, and type C2. Niemann-Pick disease type B is a mild subtype of Niemann-Pick disease, characterized clinically by onset in childhood with hepatosplenomegaly, growth retardation, and lung disorders such as infections and dyspnea. Progressive and/or clinically significant neurologic manifestations occur infrequently. The diagnosis of Niemann-Pick disease is based on detection of either biallelic pathogenic variants in SMPD1 gene or residual ASM enzyme activity that is less than 10% of peripheral blood lymphocytes or cultured skin fibroblasts. Survival to adulthood can occur.