Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare genodermatosis with onset in infancy. It results from mutations of Forkhead box P3 (FOXP3), on the X chromosome, required for development of CD4+CD25+ regulatory T cells (Tregs). Tregs are a subset of T cells with a strong immunosuppressive effect. They function in maintaining immune balance and are highly involved in the regulation of autoimmune and allergic events. When Tregs fail to function properly, a lack of immune homeostasis ensues, leading to excessive immune responses and inflammatory manifestations characteristic of the syndrome.

Affected males commonly develop type 1 diabetes mellitus (even as early as the first month of life), intractable diarrhea, malabsorption and failure to thrive secondary to autoimmune enteropathy, and atopic dermatitis. Atopic dermatitis may be accompanied by food allergies and increased immunoglobulin E (IgE) levels with associated eosinophilia.

About one-half of patients experience anemia, thrombocytopenia, or neutropenia. Other autoimmune conditions including thyroiditis and nephropathy may also present. Arthritis, alopecia areata, alopecia universalis, chronic urticaria, and bullous pemphigoid are rare.

If not treated, children with IPEX syndrome may succumb early in life due to malabsorption and failure to thrive or due to sepsis.