A Case of Para-Bombay Phenotype Caused by Homozygous Mutation of the FUT1 Gene

A 79-year-old female patient presented at the hospital with osteoarthritis. Examination of the patient revealed hemoglobin level of 10.8 g/dL, RBC count of 3.45x106/μL, WBC count of 10.1x103/μL, and platelet count of 122x103/μL. Plasma levels of blood urea nitrogen, creatinine, sodium, potassium, and alanine aminotransferase were all within the normal ranges, while aspartate aminotransferase was slightly higher than normal. A blood sample obtained from the patient was submitted to our division for blood typing and cross-matching, with a request to receive 2 units of packed red blood cells. ABO typing was performed using standard serological techniques after an immediate spin. Testing the patient’s red blood cells revealed no detectable ABO antigens upon forward/cell grouping (group O blood type). On the other hand, reverse/serum grouping showed the presence of A antibodies in the serum (group B blood type). To resolve the discrepancy between cell and serum grouping we performed an agglutination examination of anti-H serum; the red blood cells from the sample did not exhibit an agglutination reaction. Additionally, secretor status was determined in order to assess the presence of soluble blood group substances. Our results showed the presence of B and H antigens in the saliva. Based on these results, the patient in the present case was diagnosed as having a para-Bombay B phenotype (Table 1, Figure 1).