AT1R Activating Autoantibodies in Hematopoietic Stem Cell Transplantation.

Angiotensin II type 1 receptor activating autoantibodies (AT1R-AAs) have gained attention in solid organ transplant as non-HLA 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 3 post-hematopoietic stem cell transplant (HSCT) cases with patients demonstrating elevated levels of AT1R-AAs detected within the first year post-HSCT. All patients had hypertension, and 2 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 2 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.