Sirolimus is a signal transduction inhibitor with a tolerable side effect profile. Sirolimus has two properties making it an attractive agent to treat patients with autoimmune cytopenias syndromes, including ALPS. First, sirolimus induces apoptosis in normal and abnormal white blood cells, the cell type dysregulated in patients with autoimmune disease. In addition, sirolimus increases a T cell subset called Regulatory T cells (Tregs). Tregs are a cell population designed to suppress the immune system and control autoimmunity. These combined properties make sirolimus unique as compared with other immunosuppressive agents. Ample preclinical and clinical data exists demonstrating sirolimus in effective in patients with autoimmunity. Accordingly, we hypothesize sirolimus is a safe and efficacious medication for patients with autoimmune destruction of blood cells..