Immune Dysregulation, Polyendocrinopathy and Enteropathy X-Linked Syndrome with Neonatal Onset: A Case Report.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare monogenic autoimmune disorder caused by mutations in the FOXP3 gene. It typically presents in early infancy with severe multisystem autoimmunity. We report the case of a male preterm infant, born at 30 weeks' gestation, who developed enteropathy, eczema, eosinophilia, and transfusion-dependent cytopenias. Recurrent infections and a desquamative rash raised suspicion of an inborn error of immunity. Immunological studies revealed absent FOXP3 expression, and genetic testing confirmed a hemizygous pathogenic variant in FOXP3 (c.1076C>T), establishing the diagnosis. Immunosuppressive therapy with corticosteroids and sirolimus was initiated, and the patient was referred for hematopoietic stem cell transplantation. From the cases reported in the literature, this is the first neonatal onset case of IPEX reported in Portugal. This case highlights the importance of suspecting IPEX syndrome in infants with early-onset autoimmunity and immunodeficiency, enabling timely diagnosis and improved outcomes in this life-threatening condition.