Genetic CD21 Deficiency
CD21 (complement receptor 2, CR2) deficiency has been first described in 2012 by Thiel et al. in a single patient. To date, three further patients have been reported. CD21 deficiency is caused by compound heterozygous or homozygous mutations in the CD21 gene. The CD21-deficient patients may have a relatively mild clinical phenotype with recurrent bacterial infections and autoimmune-mediated myalgia or a more severe phenotype with recurrent upper and lower respiratory tract infections first presenting in early childhood. CD21 deficiency should be ruled out in patients with clinical signs of humoral immunodeficiency, hypogammaglobulinemia, and a decrease in class-switched memory B cells. The absence of CD21 expression on peripheral B cells can easily be detected by immunophenotyping.
KeywordsCD21 B cells Bacterial infections Myalgia Autoimmunity
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