Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome: A systematic review

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a monogenic disorder characterized by early onset fatal multi-system autoimmunity due to loss-of-function mutations in the gene encoding the forkhead box P3 (FOXP3) transcription factor which is crucial for the development, maturation, and maintenance of CD4+ regulatory T (T-reg) cells. Various autoimmune phenomena such as enteropathy, endocrinopathies, cytopenias, renal disease, and skin manifestations are characteristic findings in patients affected by IPEX syndrome. In this systematic review, we focus on both clinical and demographic characteristics of IPEX patients, highlighting possible genotype-phenotype correlations and address prognostic factors for disease outcome. We performed a literature search to systematically investigate the case reports of IPEX which were published before August 7th, 2017. A total of 75 articles (195 patients) were identified. All IPEX patients included had FOXP3 mutations which were most frequently located in the forkhead domain (n = 68, 34.9%) followed by the leucine-zipper domain (n = 30, 15.4%) and repressor domain (n = 36, 18.4%). Clinical manifestations were as follows: enteropathy (n = 191, 97.9%), skin manifestations (n = 121, 62.1%), endocrinopathy (n = 104, 53.3%), hematologic abnormalities (n = 75, 38.5%), infections (n = 78, 40.0%), other immune-related complications (n = 43, 22.1%), and renal involvement (n = 32, 16.4%). Enteropathic presentations (P = 0.017), eczema (P = 0.030), autoimmune hemolytic anemia (P = 0.022) and food allergy (P = 0.009) were associated with better survival, while thrombocytopenia (P = 0.034), septic shock (P = 0.045) and mutations affecting the repressor domain (P = 0.021), intron 7 (P = 0.033) or poly A sequence (P = 0.025) were associated with increased risk of death. Immunosuppressive therapy alone was significantly associated with increased cumulative survival compared to patients who received no treatment (P = 0.041). We report the most comprehensive summary of demographic and clinical profiles derived from a total of 195 IPEX patients with deleterious mutations in FOXP3. Analysis of our findings provides new insights into genotype/phenotype correlations, and clinical and genetic factors associated with increased risk of death and response to treatment strategies.