CD25 (α chain of the high-affinity IL-2 receptor) deficiency is an autosomal recessive disorder due to mutations in the IL2RA gene. T regulatory cells constitutively express CD25 and respond to IL-2 generated by T cells during an immune response for their immunoregulatory functions. CD25 deficiency results in a syndrome similar to IPEX with severe enteropathy, diabetes mellitus, autoimmune hemolytic anemia, eczema, and lymphoproliferation. Importantly, patients with CD25 deficiency exhibit several unique features not seen in IPEX, namely chronic herpetic viral infections and an increased susceptibility to infections.