Background: Autoimmune cytopenias are significant complications that can occur after pediatric solid organ transplants and often tacrolimus-induced. A variety of treatment methods have previously been investigated, however, little research has focused solely on autoimmune cytopenias in pediatric cardiac transplantation. The purpose of this study was to assess the outcomes of common treatment methods utilized in pediatric heart transplant patients presenting with autoimmune cytopenias. Methods: This single center retrospective study included all pediatric patients from 0-18 years at the time of transplant, who were diagnosed with autoimmune cytopenias following heart transplant between January 1996 and July 2019. Results: Thirteen patients (6.9%) out of 188 total heart transplant patients were diagnosed with autoimmune cytopenia (AIC). All patients received immune modulation (primarily tacrolimus) to prevent rejection and 7 of 13 patients (53%) had preceding viral infection. The median time from transplant to the diagnosis of the first episode of AIC was 3.6 years (IQR 0.7-4). The most common immune cytopenia was autoimmune hemolytic anemia (AIHA) (10/13, 76.9%). Multi-lineal cytopenias (Evans syndrome) were common and occurred in 8 cases (8/13, 61.5%; 5 cases with two lines and 3 cases with three lines). Five patients (5/13, 38.5%) were diagnosed with a single immune cytopenia. First-line therapy with steroids and/or IVIg was only successful in four cases (4/13, 30.8%): two patients with AIHA required only pulse steroids treatment; one patient with adenovirus infection and pancytopenia, and another patient with autoimmune thrombocytopenia (AITP) responded to high dose IVIg only. Overall, the majority of the cases, 8 patients (8/13, 62%) failed steroids and/or IVIg, and required second-line therapy with anti-CD20+ rituximab to achieve sustained response. This group included all 4 patients with isolated autoimmune neutropenia (AIN). Conclusions: Tacrolimus-induced AIC often requires treatment in patients with heart transplant. A subset of patients develops AIC that can be multi-lineal and require second-line therapy. In our cohort, rituximab resulted in excellent response in first-line refractory cases.. Response rates varied between treatment types and the type of autoimmune cytopenia. [ABSTRACT FROM AUTHOR]