Acid sphingomyelinase deficiency (ASMD)—also known as Niemann–Pick (NP) disease—is a rare, autosomal recessive disorder which is characterized by deficiency of the lysosomal enzyme acid sphingomyelinase (ASM), resulting in excessive storage of lipids in organs (i.e., spleen, liver, lung, bone marrow, lymph nodes, and vascular system). Only a few cases of moderate-to-severe valvular heart disease due to ASMD are described in the literature, mostly in adulthood. We report here the case of a patient with NP disease subtype B that was diagnosed during adulthood. NP disease in this patient was found to be associated with situs inversus. Specifically, a severe, symptomatic aortic stenosis was identified, and the need for surgical or percutaneous intervention was discussed. The heart team chose transcatheter aortic valvular implantation (TAVI), which was successfully performed with no complications on follow-up.