RAPID INTRAVENOUS DESENSITIZATION TO HORSE ANTITHYMOCYTE GLOBULIN IN A WOMAN WITH SEVERE APLASTIC ANEMIA

Abstract

Introduction Antithymocyte globulin (ATG) and cyclosporine is a first line regimen for the treatment of severe aplastic anemia in patients without a matched sibling donor for transplant. Administration of ATG is associated with life threatening anaphylaxis in up to 5% of post-marketing cases. Accordingly, the manufacturer's insert recommends skin testing prior to first-time administration of ATG. We present a case of a 59 year-old woman with positive skin testing to horse ATG, who underwent successful desensitization to ATG for treatment of her severe aplastic anemia. Case Description A 59 year-old woman with severe aplastic anemia was admitted to our institution for induction therapy with ATG and cyclosporine. Pre-treatment skin testing to ATG was positive, with a 13 mm wheal after intradermal injection of 5 mcg of ATG. Epicutaneous skin testing was negative. She underwent successful rapid intravenous desensitization to ATG with no adverse reactions during the procedure. She completed a four-day cycle of ATG and was started on daily cyclosporine. She had good response to ATG treatment, and at six-month follow-up, she had continued clinical remission sustained with cyclosporine and eltrombopag. Discussion Our patient's positive intradermal skin testing was suggestive of a Type I hypersensitivity to ATG. Patients with positive skin testing should avoid ATG or undergo desensitization when medically necessary. Previous reports have described several cases of life threatening hypoxia and hypotension during ATG desensitization, but our patient successfully underwent a rapid intravenous desensitization and subsequently tolerated a four-day continuous infusion of ATG.