RESUMEN
H-antigen deletion is often caused by FUT1 gene mutation, which is a very rare blood group. In this case, the H-antigen phenotype, FUT1, FUT2 sequences, and family genetic investigation of a 26-year-old patient (proband) and her three family members were studied. The results showed that the proband and little her brother were H-deficient phenotype, their ABO genotype of both was A/O1, her father was A/B, and her mother was O1/O1. The proband and her little brother's FUT1 phenotype were both h3|h3, with a homozygous mutation 658C > T in their FUT1 gene, and the FUT1 phenotype of their parents' were H|h3, with a heterozygous mutation (658C > T) in their FUT1 gene. The result of whole gene sequencing showed that the father of the proband had a deletion of CHR19.49,255,178-49,257,177 in the FUT1 gene (hg19 was used as the reference). The results of the family investigation showed that the mutation of site 658 in the FUT1 gene between offspring and parents was consistent with Mendelian inheritance law.