Objective:To investigate the serological and molecular genetic characteristics of a voluntary blood donor with combined FUT1 and ABO blood group gene variants causing para-Bombay and A2 subtype, and to review relevant literature on para-Bombay blood types carrying alleles such as FUT101W.37 and FUT101W.23. Methods:A blood donor with para-Bombay and A 2 subtype who participated in voluntary blood donation at the Dongguan Blood Center in August 2023 was selected as the study subject. Serological tests were performed to identify the ABO blood group, Lewis blood group antigens, and unexpected serum antibodies in the donor. Adsorption-elution test was conducted to detect trace antibodies in the blood donor′s plasma to trace the A, B and H antigens on the red blood cell surface. Sanger sequencing was carried out to analyze the sequences of the FUT1 and ABO genes. Using keywords such as " para-Bombay" " FUT1*01W.37" and " FUT1*01W.23" both in Chinese and English, relevant literature on para-Bombay blood type subjects carrying FUT1*01W.37 and FUT1*01W.23 alleles was retrieved from the CNKI, Wanfang Data Knowledge Service Platform, and PubMed databases, and the retrieval time was set as from the establishment of database to December 2022. This study has been approved by the Ethics Committee of Dongguan Blood Center (No. 2022005), and informed consent of blood donation was obtained from the blood donor. Results:Serological testing of the blood donor revealed inconsistent results between forward and reverse ABO blood typing, negative H antigen on the red blood cell surface, Le(a-b+ ) secretor type for Lewis blood group, and unexpected anti-H antibodies in the plasma, indicating a suspected para-Bombay type. Absorption-elution test suggested the blood type of the blood donor to be para-Bombay and A subtype. Sanger sequencing showed that the donor has harbored homozygous FUT1*(c.35T+ c.803A)/(c.35T+ c.803A) variant, with the FUT1*(c.35T+ c.803A) allele containing a dual nucleotide variant unrecorded by the International Society of Blood Transfusion (ISBT) FUT1 gene variant database, which was similar to the weakly functional allele of FUT101W. 37(c.803G>A) as recorded by the ISBT database. The ABO genotype was heterozygous ABOA2.05/O.01.02. Combining the results of serological and genetic testing, the blood type of the blood donor was determined to be para-Bombay and A 2 subtypes. Literature review has identified a pregnant women from Qingdao carrying the FUT1*01W.37 allele and 2 individuals carrying a heterozygous FUT1*01W.23 allele. Conclusion:This study has discovered a blood donor with coexisting para-Bombay and ABO subtype blood groups. Based on the characteristics of red blood cell surface antigens, the FUT1*01W.37 as classified as an FUT1 null allele.

The proband was a 33-year-old pregnant woman (G4P1) who suffered spontaneous abortion in the first 3 months of pregnancy without a history of blood transfusion or transplantation. The fourth pregnancy was clinically diagnosed with threatened abortion, and a cesarean section was performed on June 28, 2023, at the Obstetrics and Gynecology Department of Dongguan Hospital of Traditional Chinese Medicine. During cross-matching tests, unexpected antibodies were detected in the proband′s plasma, which could not be specifically identified, and no suitable donor red blood cells could be found. The blood samples were sent to the Blood Transfusion Laboratory of Dongguan Blood Center. The laboratory used serology to identify the erythrocyte phenotype of the proband and confirmed the proband as having a rare p blood group. The unexpected antibody was identified as anti-PP1P K, and gene sequencing of the proband revealed that the new allele A4GALT* (c.100G>A+c.418_428delins) was homozygous, which is speculated to cause changes in the polypeptide chains p.Veral34ile and p.GERln140TRPFS *73, and inactivation of α1, 4-galactosyltransferase. At the same time, another new allele A4GALT*c.100G>A was found in family members, and it was predicted that the single change of p.Val34Ile caused by this mutation would not affect protein function or enzyme activity.