Early-onset refractory diarrhea due to immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome associated with a novel mutation in the FOXP3 gene: A case report

BACKGROUND: Immune dysregulation, polyendocrinopthy, enteropathy, X-linked (IPEX) syndrome is a rare X-linked recessive disease caused by mutations in the forkhead box protein 3 (FOXP3) gene, which is a master transcriptional regulator for the development and function of CD4(+)CD25(+) regulatory T (Treg) cells. The dysfunction of these cells leads to multiple system autoimmune diseases. We present a case of IPEX due to a mutation not reported in the literature before. CASE SUMMARY: We report a male patient with IPEX syndrome who presented with refractory diarrhea and malabsorption leading to failure to thrive, as well as with hypothyroidism and nephrotic syndrome. Laboratory investigation showed increased total IgE and Treg cells, decreased free triiodothyronine (FT3) and free thyroxine (FT4), and proteinuria. Multiple dietary and supportive treatments were introduced but did not improve the diarrhea during his hospital stay. Ultimately, whole exome sequencing revealed that the patient was hemizygous for the exon 5, c.542G>A (p.Ser181Asn) mutation of the FOXP3 gene, which has not been previously reported. The patient remains on prednisone and euthyrox while awaiting hematopoietic stem cell transplantation at the time of the compilation of this case report. CONCLUSION: We report a novel FOXP3 gene mutation involved in IPEX. A high level of suspicion should be maintained in an early-onset refractory diarrhea patient.