Niemann-Pick disease (NPD) A/B is a lysosomal storage disease (LSD), caused by an autosomal recessive disorder that causes variation in sphingomyelin phosphodiesterase-1 (SMPD1). Systemic signs are cholestatic jaundice in the neonatal period or hepatosplenomegaly in infancy. The clinical course experienced by our patient did not correspond to the classic phenotypes. The diagnosis was effectively made at four years and three months of age when different signs such as abdominal distension, hepatosplenomegaly, and chronic malnutrition were present. Given the high suspicion of metabolic storage disease, an enzyme activity study, liver and bone marrow biopsies, and molecular studies were performed. In the bone marrow biopsy, pseudo-Gaucher foam cells were observed. Additionally, the liver biopsy showed dispersed ballooned cells with deposit material and nested cells with granular material. The double enzymatic assay was ordered to determine if the cause of these findings was due to Niemann-Pick or Gaucher disease; decreased sphingomyelinase activity values were obtained (0.28 mcoml/L/h). Subsequently, the molecular genetics study reported a double alteration in the sequence that encodes the SMPD1 gene, located on chromosome 11p15.4, which confirmed NPD type A or B. The overlap and the lack of some findings made the diagnosis very difficult. Diagnosis is crucial due to the multisystem involvement that this LSD can have.