EFO_0020902 (bombay phenotype) can be described as follows. Two main types of recessive c phenotypes are recognized: (1) the nonsecretor classic Bombay type (h null and se (FUT2; 182100) null) with H deficiency of both red cells and saliva, and (2) the secretor Bombay type (h null, Se heterozygous) with H deficiency in red cells but normal ABH in secretions. The latter has been designated para-Bombay phenotype. Under this 2-locus model, the H blood group locus determines expression of the H antigen (as well as the A and/or B antigens) in the erythroid lineage, whereas the SE locus controls H expression (and thus A or B antigen expression) in a variety of secretory epithelia and in saliva. Bombay and para-Bombay individuals display no apparent deleterious phenotype except in circumstances requiring blood transfusion, wherein they are cross-match incompatible with all donors except other H-deficient individuals.