First molecularly characterized Para‐Bombay phenotype in Iraq: Clinical, serological and genetic insights with implications for transfusion safety

Vollständiger Abstract

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Abstract Background 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. Study Design and Methods 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. Results 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). Discussion 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.