Deletion in the A4GALT Gene Associated with Rare "P null" Phenotype: The First Report from India

Abstract

Background: The present report illustrates a case with rare "P null" phenotype due to a large deletion in chromosome 22q13.2 and with clinically significant anti-PP1P^k antibody. Patient blood management in such cases is challenging.

Case report: The transfusion center supporting the tertiary care referral center in the southern part of India received a blood sample from a trauma case for pre-transfusion testing. An antibody to a high-frequency blood group antigen was initially suspected. Following extensive immune-hematological workup, the patient was diagnosed to have naturally occurring anti-PP1P^k antibody and a rare "P null" phenotype. The genomic DNA of the patient was analyzed by exome sequencing followed by Sanger's sequencing. Molecular diagnostics revealed a large 21-bp deletion in chromosome 22q13.2 which encodes the A4GALT gene, resulting in truncation of seven amino acids I245-251P and resulted in rare "P null" phenotype. Patient blood management strategies were adopted to manage the patient conservatively without blood transfusion.

Conclusion: A large deletion in chromosome 22q13.2 had resulted in a rare "P null" phenotype in the present case. The patient was a victim of a road traffic accident, required emergency hospitalization, as well as surgical intervention, and his plasma had antibodies to high-frequency antigens. A rare donor registry plays a major role in providing transfusion support to such cases.

Keywords: A4GALT gene; Anti-PP1Pk; Blood transfusion; Large deletion; Null phenotype; Patient blood management; Rare blood group.