BACKGROUND AND OBJECTIVES: Individuals with the rare p phenotype have red cells lacking P, P1 and P MATERIALS AND METHODS: Samples from a 32-year-old Indian blood donor were investigated due to the presence of a pan-reactive alloantibody, together with samples from his sister and mother. Standard serological investigations and A4GALT sequencing were performed. RESULTS: The donor was found to have p phenotype, and his plasma contained anti-PP1P CONCLUSION: We have identified homozygosity for a novel A4GALT null allele (carrying c.526G>
A, p.Asp176Asn), resulting in lack of functional 4-α-galactosyltransferase and a p phenotype, adding to the catalogue of known genetic backgrounds of this rare phenotype.