Development of warm autoimmune hemolytic anemia after initiation of Ruxolitinib in a patient with STAT1 gain-of-function mutation

Abstract

IntroductionSTAT1 gain-of-function (GOF) disease is associated with chronic mucocutaneous candidiasis (CMC) and a broad spectrum of infectious, inflammatory, and vascular manifestations. The Janus Kinase inhibitor ruxolitinib has been used successfully for CMC and autoimmune phenomena. We describe a case of warm autoimmune hemolytic anemia (WAIHA) in a patient with STAT1 GOF disease after initiating ruxolitinib. Case reportA 36-year-old man with STAT1 c.850G>A (p.Glu284Lys) mutation presented with CMC as well as recurrent viral and bacterial infections, lymphadenopathy, enteritis, nodular regenerative hyperplasia (NRH) and splenomegaly. Immune workup confirmed a combined immunodeficiency with hypogammaglobulinemia and T-cell lymphopenia. Ruxolitinib was initiated at 5 mg twice daily (due to pre-existing thrombocytopenia) with up titration over 3 months to 20 mg twice daily. He improved with weight gain, increased energy, resolution of chronic anemia, and improved lymphadenopathy and splenomegaly on imaging. Serum CXCL9 only minimally decreased from 4660 pg/ml to 3990 pg/ml. Soon after reaching ruxolitinib 20 mg twice daily, he developed JC viremia, prompting dose reduction to 15 mg BID. Within two weeks, he developed a non-COVID upper respiratory tract infection followed by fatigue, shortness of breath with ambulation, and dark urine. Emergency evaluation revealed warm antibody positive hemolytic anemia with a hemoglobin of 5 g/dL, and worsened thrombocytopenia. He was treated with blood transfusions, pulse steroids, and high-dose IVIG with stabilization but continued hemolysis. Due to the JC viremia, there was concern to give rituximab with increased PML risk. Bone marrow showed trilineage hematopoiesis, a mild increase in megakaryocytes and RBC precursors, and a loss of B-cell progenitors with retention of mature B cells. His B and T lymphocyte numbers had increased since prior to ruxolitinib, with a predominance of Tfh1-cells (58.7% of total Tfh-cells). He was started on sirolimus with a slow taper of prednisone with continued stable hemoglobin and platelets, and resolution of hemolysis after 3 months. ConclusionTo our knowledge, this is the first case of a STAT1 GOF patient developing WAIHA while receiving ruxolitinib therapy. Treatment choices were complicated by the risks of PML. Sirolimus combined with ruxolitinib allowed wean of corticosteroid and subsequent resolution of hemolysis.