MHC-II deficiency in a large Algerian cohort: Clinical, immunological, and genetic characterization

MHC class II (MHC-II) deficiency is a rare inborn error of immunity caused by defects in transcriptional regulators of MHC-II expression. In this study, we characterized the clinical, immunological, and molecular features of 107 patients from 98 unrelated Algerian families. Median ages at symptom onset and diagnosis were 5 and 14 mo, respectively, with pneumonia (82%) and chronic diarrhea (73%) predominating. CD4+ T cell lymphopenia occurred in 87.6% and naïve CD4+ T cell depletion in 86.0%. Among 99 genetically characterized patients, variants were identified exclusively in RFXANK (77.8%) and RFXAP (22.2%), including two predominant mutations (RFXANK c.338-25_338del and RFXAP c.368del) and four novel variants. Exploratory comparisons suggested a more severe phenotype in patients carrying RFXAP c.368del than in those carrying RFXANK c.338-25_338del. Five of seven transplanted patients survived versus 33.3% of non-transplanted patients. As the largest MHC-II deficiency cohort reported to date, this study substantially expands current knowledge of the disease and supports targeted genetic diagnosis in North African populations.