Red blood cell alloimmunization in transfused patients with hereditary hemorrhagic telangiectasia: A single centre...

Hereditary hemorrhagic telangiectasia (HHT) is a genetic blood vessel disorder which may lead to chronic bleeding and red blood cell (RBC) transfusions. Data on transfusion requirements and complications in HHT patients are sparse.

Retrospective chart review was conducted at St. Michael's Hospital (SMH) in Toronto, Canada. All adults with a definite clinical diagnosis of HHT AND inpatient hospital visits between January 1, 2011 and December 31, 2020 AND had undergone transfusion compatibility testing at SMH, were identified. Data were abstracted from electronic medical records. Simple descriptive statistics were used to analyze data. Institutional Research Ethics Board approval was obtained.

63 HHT patients underwent compatibility testing and were subsequently transfused at SMH. Median patient age at data abstraction was 70 years (Interquartile Range [IQR]: 18) and 35 (56 %) were female. RBC alloantibodies were found in 23 transfused patients (36.5 %) and were predominantly directed against Rh and Kell antigens: Anti-E (65 %), Anti-K (39 %) and Anti-c (22 %) were most common. Excluding an outlier who received 611 RBC units during the study period, the mean number of RBC units transfused per HHT patient at SMH was 22.1 units (Standard Deviation: 40.9, IQR: 17). Six (9.5 %) transfused patients experienced at least one transfusion reaction.

RBC alloimmunization rate was 36.5 % in our cohort of transfused HHT patients; this is much higher than described in the general population and another transfused HHT cohort. The most commonly observed alloantibodies were Rh and Kell, supporting our policy of prophylactic phenotypic matching for these antigens for all transfused patients with HHT.