Abstract
Background: IPEX syndrome ir a rare monogenic autoimmune disorder resulting from mutations in the FOXP3 gene. This condition is typified by severe early-onset autoimmunity, typically presenting as a triad encompassing enteropathy, polyendocrinopathy, and eczema. Renal involvement is less common.
Case Description: One-year-old male exhibiting enteropathy, endocrinopathy, Fanconi syndrome-type proximal renal tubular acidosis, and recurrent infections. Given the suspicion of autoimmune multisystemic syndrome versus autoimmune polyendocrine syndrome, exome sequencing was conducted, revealing a pathogenic mutation in the FOXP3 gene (c.227 del; p.Leu76GlnfsTer53) associated with IPEX syndrome. Additionally, a variant of uncertain significance in the MRTFA gene (c.446C>T; p.Ser149Leu) was identified.
Our patient manifested an early presentation of IPEX syndrome, displaying two cardinal features along with recurrent infections and renal involvement in the form of proximal tubular acidosis-type autoimmune Fanconi syndrome. This was characterized by metabolic acidosis with a normal serum anion gap, positive urinary anion gap, hypokalemia, hypophosphatemia, glucosuria and proteinuria, requiring electrolyte replacement and Shohl's solution.
Conclusion: Autoimmune Fanconi syndrome secondary to IPEX syndrome is a rare manifestation, with our identified mutation implicated in the presented phenotype. This case highlights the presentation of Fanconi syndrome to debut in IPEX syndrome, in addition to the classically triad proposed in the literature.