AT1R Activating Autoantibodies in Hematopoietic Stem Cell Transplantation

Abstract Angiotensin II type 1 receptor activating autoantibodies (AT1R-AA) have gained attention in solid organ transplant as non-human leukocyte antigen antibodies associated with rejection, vasculopathy, and graft dysfunction. These antibodies have also been reported in the context of pre-eclampsia, scleroderma, and isolated hypertension. Here, we present three post-hematopoietic stem cell transplant (HSCT) cases with patients demonstrating elevated levels of AT1R-AA detected within the first year post-HSCT. All patients had hypertension, and two patients exhibited profound diarrhea and hypokalemia. The hypertension, in all cases, was refractory to multiple classes of antihypertensives. Upon autoantibody identification, an angiotensin receptor blocker, losartan, was promptly initiated, and all patients showed blood pressure improvement. The two patients with electrolyte disturbances had rapid normalization of these levels and resolution of the diarrhea. These cases demonstrate a previously unreported association of elevated AT1R-AA levels in post-HSCT patients with a rapid response to angiotensin receptor blockade initiation.