According to the Online Mendelian Inheritance in Man database (OMIM: https://www.omim.org/), HS is classified into five subtypes associated with five different genes responsible for the deficiency or dysfunction of red blood cell membrane proteins, including ankyrin 1 (ANK1; MIM #18200 [SPH1]), β-spectrin (SPTB; MIM #616649 [SPH2]), α-spectrin (SPTA1; MIM #270970 [SPH3]), band 3 protein (SLC4A1; MIM #612653 [SPH4]), and protein 4.2 (EPB42; MIM #612690 [SPH5]) (Supplemental Table S1). The gene discussed is SLC4A1; the disease is histiocytic sarcoma.