D-- phenotype in a South Indian family: A multicentric approach to workup and management

The Rh system is an extremely important blood group system with over 50 antigens, 5 of which (D, C, E, c and e) are considered most clinically significant. Rare Rh deficient phenotypes include D--, which is a blood group characterised by the lack of expression of C, c, E and e and exalted expression of the D antigen on the red cells due to mutations in both alleles of the RHCE gene. This is a multicentre approach to a case of the rare D-- phenotype.

A 56-year-old lady with bad obstetric history presenting with severe anaemia had to be evaluated for a panreactive antibody affecting cross-matching. On identifying a D-- phenotype by serology, a thorough family study was performed on 18 of her first and second-degree relatives. Three family members were also found to be of the rare phenotype, one of whom was pregnant. This relative was counselled appropriately and provided with an overview of her phenotype for her obstetric care team. Molecular analysis by QMPSF confirmed the serological findings. This case eventually became the motivation behind an institutional "rare donor" registry programme.

Serology revealed a panreactive antibody affecting cross-matches. Her Rh phenotype was D+, C-, c-, E-, e-, K-, k+. Molecular analysis on her and three family members suggested homozygous CE-D hybrid alleles causing the D-- phenotype: RHCE-D(3-9)-CE.

D-- is an uncommon phenotype and was found to occur in a cluster in this family. Like most difficult immunohematological cases, it mandated a multicentric and a multi-technique approach to resolve.