An update on the H blood group system.

This update of the H blood group system (Scharberg EA, Olsen C, Bugert P. The H blood group system. Immunohematology 2016;32:112-8) reports 11 new FUT1 null alleles: 8 causative for the H- phenotype (Bombay phenotype, Oh), 3 in para-Bombay cases, and 5 new FUT1 alleles causative for a weak H phenotype (para-Bombay, H+w). The H blood group system (International Society of Blood Transfusion system 18) consists of a single antigen (H) defined by a terminal fucose residue found on red blood cells (RBCs) and in secretions. The H antigen is synthesized on the RBC surface by the FUT1 gene product fucosyltransferase 1. On epithelial cells and in body fluids, the H antigen is synthesized by the FUT2 gene product fucosyltransferase 2.