Case Report IPEXSyndromewithNormalFOXP3ProteinExpressioninTreg CellsinanInfantPresentingwithIntractableDiarrheaasa Single Symptom AliAlMaawali, 1 Beata Derfalvi, 2 JohanVanLimbergen, 3 Andrew Issekutz, 2 Thomas Issekutz, 2 Hasan Ghandourah, 1 andMohsinRashid 1 1 Department of Paediatrics, Faculty of Medicine, Dalhousie University, IWK Health Centre, Halifax, Nova Scotia, Canada 2 Division of Immunology, Department of Paediatrics, Faculty of Medicine, Dalhousie University, IWK Health Centre, Halifax, Nova Scotia, Canada 3 Division of Pediatric Gastroenterology and Nutrition, Emma Children’s Hospital, Amsterdam University Medical Centers, Amsterdam, Netherlands Correspondence should be addressed to Mohsin Rashid; mohsin.rashid@iwk.nshealth.ca Received 29 December 2019; Revised 4 July 2020; Accepted 2 September 2020; Published 9 September 2020 Academic Editor: Jiri Litzman Copyright © 2020 Ali Al maawali et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. IPEX (immune dysregulation-polyendocrinopathy-enteropathy-X-linked) syndrome is a rare, potentially fatal multisystem disorder caused by mutations in the FOXP3 gene. is can lead to quantitative or functional deficiency of regulatory Tcells (Treg), thereby affecting their immune-suppressive actions which can in turn cause autoimmune and inflammatory disorders. We describe an infant with IPEX syndrome with unremarkable maternal family history whose only presentations were severe diarrhea and malnutrition. e patient had a normal percentage of Treg cells and FOXP3 protein expression, but further testing revealed a hemizygous missense mutation in the FOXP3 gene. IPEX syndrome should be considered in young children even if severe intractable diarrhea is the only symptom with no other autoimmune manifestations. Sequencing of the FOXP3 gene should always be considered for accurate diagnosis to look for mutations even in the face of normal FOXP3 protein expression in the Treg cell. 1.Introduction IPEX (immune dysregulation-polyendocrinopathy-enter- opathy-X-linked) syndrome is a rare multisystem disorder that often presents in early childhood and can be fatal. It was first described by Powell et al. in 1982 [1]. Immune dys- regulation is the hallmark of this disorder. Human immu- nological self-tolerance on the periphery is controlled by a subset of T lymphocyte cells called the regulatory (Treg) cells [2]. ey play a pivotal role in suppressing autoimmunity and atopy by suppressing self-reactive lymphocytes and preventing excessive reactions to self- and foreign antigens [2, 3]. e Treg cell development and function are dependent on the expression of a protein called forkhead box protein 3 (FOXP3). FOXP3 is a transcription factor located on chromosome Xp11.23 and is considered a master switch gene for these Treg cells. e absence or dysfunction of FOXP3 can cause qualitative or functional deficiency of Treg cells, thus leading to immune dysregulation and IPEX syndrome [2–5]. IPEX syndrome can be misdiagnosed and hence may be underreported [6]. 2.CasePresentation A 5-month-old male was admitted with severe diarrhea and failure to thrive. e baby was born at term after an un- eventful pregnancy and delivery with a birth weight of 2.97 kg. He was exclusively breast-fed. At 2-1/2 months of age, he developed frequent, large volume, watery stools with occasional blood streaks. ere was no fever, emesis, or any infectious contacts. e family history was only significant for two paternal second-degree relatives with celiac disease and one-second degree relative with a thyroid disorder and type 1 diabetes mellitus. Hindawi Case Reports in Immunology Volume 2020, Article ID 9860863, 5 pages https://doi.org/10.1155/2020/9860863