EPB42 encodes erythrocyte membrane protein band 4.2, a structural component of the red blood cell membrane cytoskeleton that functions within the ankyrin-1 complex to maintain erythrocyte membrane stability and shape 1. The protein exhibits protein-glutamine gamma-glutamyltransferase activity and is part of a transglutaminase gene cluster on chromosome 15 2. EPB42 expression is specifically associated with hematopoiesis, distinguishing it from other transglutaminase family members that show broader tissue distribution 2. Pathogenic variants in EPB42 cause hereditary spherocytosis type 5, though EPB42 mutations are relatively uncommon, accounting for only 4% of hereditary spherocytosis cases in Chinese populations 3. The variants are predominantly missense mutations, with one variant (p.Gln377His) identified as a potential hotspot 3. Clinically, patients with EPB42 variants tend to present with milder hereditary spherocytosis phenotypes compared to those with SPTA1 or SPTB mutations 4. Interestingly, EPB42 has also been identified as a prognostic biomarker in acute myeloid leukemia, where high expression correlates with favorable outcomes in FLT3-ITD-negative patients 5.