C0623 - Severe Transplantation-Mediated Alloimmune Thrombocytopenia After Liver Transplant Treated Successfully With Efgartigimod

R. Christopher Chase, MD, Andree H. Koop, MD, Denise M. Harnois, DO, Jennifer J. O'Brien, MD, PhD, Nicole M. Loo, MD
Mayo Clinic, Jacksonville, FL

Introduction: Transplantation-mediated alloimmune thrombocytopenia (TMAT) is a rare form of passenger lymphocyte syndrome in which lymphocytes from the donor organ produce antibodies against recipient platelets resulting in thrombocytopenia. We describe a novel treatment of TMAT with efgartigimod, a human IgG1 Fc antibody fragment, in a patient with severe, refractory thrombocytopenia following liver transplantation.

Case Description/Methods: A 70-year-old man with cirrhosis secondary to non-alcoholic steatohepatitis complicated by hepatocellular carcinoma underwent deceased donor orthotopic liver transplantation. He required emergent retransplantation on post-operative day 7 for acute hepatic artery thrombosis. Seven days after retransplantation, the patient developed severe thrombocytopenia with platelets < 1x10⁹/L. He responded poorly to platelet transfusion, and two days later developed severe intra-abdominal bleeding requiring exploratory laparotomy. No active bleeding was found, and splenectomy was performed. Testing for heparin induced thrombocytopenia was negative, and the working diagnoses were post transfusion purpura and idiopathic thrombocytopenic purpura. Over the next 8 weeks, the patient had persistent, severe thrombocytopenia despite platelet transfusions and treatment with intravenous immunoglobulin, plasmapheresis, rituximab, romiplostim, and eltrombopag. Notably, two patients who received lung and kidney transplants from the same donor also developed severe thrombocytopenia. Ultimately, testing revealed the presence of serum antibodies to human platelet antigen (HPA) 1a. Genetic testing revealed the genotypes HPA 1a/1b and HPA 1b/1b in the patient and donor respectively, consistent with a mismatch and TMAT. The patient received weekly efgartigimod for 4 doses, and after his third infusion developed sustained improvement in platelets to >100x10⁹/L without need for transfusion.

Discussion: TMAT is a rare disorder after solid organ transplantation that can lead to severe thrombocytopenia with life threatening bleeding and even death. Although TMAT generally resolves a few months after transplantation as donor lymphocytes are cleared from the circulation, initial management is challenging. Efgartigimod is a novel treatment approved by the food and drug administration for myasthenia gravis that leads to degradation of IgG by binding to the neonatal Fc receptor and should be considered for severe TMAT.


Disclosures:


R. Christopher Chase, MD, Andree H. Koop, MD, Denise M. Harnois, DO, Jennifer J. O'Brien, MD, PhD, Nicole M. Loo, MD. C0623 - Severe Transplantation-Mediated Alloimmune Thrombocytopenia After Liver Transplant Treated Successfully With Efgartigimod, ACG 2022 Annual Scientific Meeting Abstracts. Charlotte, NC: American College of Gastroenterology.