First molecularly characterized Para-Bombay phenotype in Iraq: Clinical, serological and genetic insights with...

H-deficient states are important in ABO-related transfusion practice. Patients may be misclassified as group O if testing stops at forward ABO typing. Anti-IH may render group O units incompatible and increase hemolysis risk.

A 70-year-old Iraqi man was referred for failure to obtain compatible blood before knee arthroplasty. ABO testing, crossmatching, antibody screening, anti-H lectin testing, saliva inhibition and molecular analysis of fucosyltransferase 1 (FUT1) and fucosyltransferase 2 (FUT2) were performed.

Forward grouping showed anti-A/anti-B 0 (apparent O), with reverse grouping 4+ with A and B cells. Multiple group O units showed immediate 4+ incompatibilities at room temperature (RT). Antibody screening was pan-reactive at RT, 37°C, and the antihuman globulin phase; the direct antiglobulin test and auto-control were negative. Patient red blood cells were nonreactive with anti-H lectin (Ulex europaeus), while control O cells reacted 4+. Cord O cells were nonreactive. Saliva inhibition demonstrated soluble H and B substances. Exome testing identified a homozygous FUT1 frameshift with wild-type FUT2; the variant is deposited in ClinVar (Variation ID 4526453).

Based on Iraqi National Blood Transfusion Center records, this is the first documented molecularly characterized Para-Bombay phenotype in Iraq. Apparent group O with O-unit incompatibility should trigger anti-H lectin testing, secretor evaluation, and molecular confirmation/referral, underscoring the need for rare-donor pathways.