Beyond the Classical Triad: Atypical Presentations and Regulatory T Cell Phenotyping in a Cohort of IPEX Patients.

Abstract

Background: Immune dysregulation, polyendocrinopathy, enteropathy, and X-linked(IPEX) syndrome caused by FOXP3 mutations is rare. FOXP3 is a transcription factor required for the regulatory T cell (Treg) development/function.

Aim: We aimed to characterize the clinical, immunologic, and genetic features of a single-center cohort of IPEX syndrome.

Patients and methods: We present the clinical/immunological/genetic features of 12 patients with IPEX syndrome. We used whole exome and Sanger sequencing for the diagnosis/familial segregation. We performed immunophenotyping and measured Treg percentage and FOXP3 expression in peripheral blood by flow cytometric analysis.

Results: Median age at diagnosis was 2.5 years (range: 0.3-22 years). Common clinical manifestations were infections (n = 9, 75%), allergies (n = 8, 67%), autoimmunity (n = 7, 58%), enteropathy (n = 7, 58%), and lymphoproliferation (n = 3, 25%). Atypical initial presentations included class IV lupus nephritis, a SCID-like immunophenotype (CD3⁺ T cells: 4% [100/µL]; CD4⁺ T cells: 3%, CD8⁺ T cells: 1%, CD19⁺ B cells: 81%, CD16/56⁺ NK cells: 13%), and isolated hypogammaglobulinemia persisting for years during follow-up. At the time of diagnosis, three (25%) patients had leukopenia, six (50%) had lymphopenia and two (17%) had neutropenia. Eosinophilia was observed in 42% of patients (25% mild, 17% moderate). Six different variants in FOXP3 were characterized in 12 patients from nine unrelated families. Four (33%) patients underwent hematopoietic stem cell transplantation (HSCT). Overall, three (25%) patients died due to infections. One patient died due to HSCT-related catheter complications, one patient died in an accident. Among the transplanted patients, two are alive and well. Among the non-transplanted patients, five are alive and are being followed up at our center. Treg (CD4⁺CD127^-/lowCD25⁺Foxp3⁺) percentage was low in eight patients compared to healthy controls (p < 0.001). FOXP3 expression was low in all the patients compared to healthy controls.

Conclusion: Atypical presentations make the diagnosis of IPEX syndrome challenging. This study expands the current knowledge of IPEX syndrome by describing a single-center cohort with certain atypical manifestations and by confirming previously reported rare phenotypes. Elucidating the genetic basis of immunodeficiency diseases contributes to improving diagnostic approaches and patient management.