A novel association between high red blood cell alloimmunization rates and hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder associated with multiple arteriovenous malformations. HHT patients may require red blood cell (RBC) transfusion due to spontaneous hemorrhage or surgical bleeding. Because HHT-associated hemorrhage often occurs in submucosa we hypothesized that RBC alloimmunization rates in HHT patients may be higher than those observed in other transfused patients and investigated this in a retrospective study.

Eighty-five patients with HHT who were transfused at our tertiary care facility were identified. A group of randomly selected, chronically transfused patients without HHT were used as controls (n = 207). RBC transfusion and alloantibody data were extracted from medical records.

Alloimmunization rates among patients with HHT were significantly higher than those of controls (15.29% vs. 2.42%; p < 0.001), while HHT patients received fewer RBC transfusions at our institution compared to controls (4.27 units vs. 8.84 units; p < 0.0001). Anti-E, -K, and -c were the three most common alloantibodies identified in HHT patients. There was a trend for HHT patients to make more antibodies per alloimmunized patient than controls (2.38 alloantibodies vs. 1.60 alloantibodies), although this difference was not significant (p = 0.37).

To our knowledge, this is the first study to evaluate RBC alloimmunization rates in patients with HHT. It is unclear whether the high alloimmunization rates observed are due to lifetime transfusion burden, underlying disease pathophysiology, or other variables. Additional studies are needed to evaluate the generalizability of our findings to other HHT populations and to consider the utility of prophylactic antigen matching for C/E/K.