![]() ![]() ![]() 2, 4, 5 Respiratory insufficiency, failure to thrive, and organ dysfunctions ensue, frequently causing death in childhood. ![]() 3-5 Infections generally occur in the first year of life and involve the respiratory and gastrointestinal tracts. 2 Impaired T- and B-cell immunity results in susceptibility to a broad range of viral, bacterial, fungal, and protozoan infections. Hypogammaglobulinemia and low CD4 T-cell counts are found in most patients. 1 This leads to defective CD4 T-cell development and function and a lack of Th cell–dependent Ab production by B cells. The lack of MHC class II expression leads to impaired antigen presentation by HLA-DR, HLA-DQ, and HLA-DP molecules on APCs such as dendritic cells and macrophages. ![]() Major histocompatibility complex (MHC) class II expression deficiency is a rare primary immunodeficiency (PID MIM 209920) that is inherited as an autosomal-recessive trait. However, some patients may survive for relatively long periods if multiple prophylactic measures are implemented. RFXANK deficiency is a severe, often fatal CID for which HSCT is the only curative treatment. However, 7 patients who did not undergo HSCT (at ages of 6-32 years) are still alive on Ig treatment and antibiotic prophylaxis. Five of the patients from this cohort who did not undergo HSCT had a poor prognosis and eventually died (at ages of 1-17 years). Ten of the 23 patients who underwent hematopoietic stem cell transplantation (HSCT) were cured, with the recovery of almost normal immune functions. We describe here the genetic, clinical, and immunologic features of 35 patients from 30 unrelated kindreds from North Africa sharing the same RFXANK founder mutation, a 26-bp deletion called I5E6-25_I5E6 + 1), and date the founder event responsible for this mutation in this population to approximately 2250 years ago (95% confidence interval : 1750-3025 years). Autosomal-recessive mutations in the RFXANK gene account for two-thirds of all cases of MHC class II deficiency. Inherited deficiency of major histocompatibility complex (MHC) class II molecules impairs antigen presentation to CD4 + T cells and results in combined immunodeficiency (CID). ![]()
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