Polyagglutinability phenomenon: a case report and review of the literature

BACKGROUND: Polyagglutinability of red blood cells is a rare immunological phenomenon, it is due to a cryptic antigen that is abnormally present on the surface of red blood cells. The aim of our work is to shed light on polyagglutinability, which is still poorly understood cause of discordance between the cell and serum tests and can sometimes have harmful transfusion consequences. CASE PRESENTATION: We report the case of a 70-year-old African patient admitted for management of hemolytic anemia. RESULTS: During the erythrocyte grouping, a discordance between the cell and serum tests was observed, with polyagglutinability for the RH phenotype, a positive AB control, and even a positive control. The direct antiglobulin test and the Coombs test were also positive. The same results were obtained even after washing the red blood cells and incubating them at 37 °C for 30 min. For transfusion purposes, erythrocyte genotyping was performed, and the patient was transfused with an A+ red blood cell unit with an RH Kell-compatible phenotype. CONCLUSION: Polyagglutinability should always be taken into account when grouping anomalies are encountered. Although it may not show any symptoms, hemolysis is frequently observed during transfusions.