Rare autosomal recessive immunodeficiency syndrome (combined immunodeficiency/CID) caused by mutation in the CD70 gene (602840) on chromosome 19p13. Immunodeficiency is characterized by increased susceptibility of B cells to Epstein-Barr virus (EBV) infections. Ghosh S et al (2020) identified a total of 16 different mutations inCD27 and 8 in CD70, respectively, based on clinical data from 49 patients from 29 families (CD27, n = 33; CD70, n = 16). The majority of patients (90%) were EBV positive at diagnosis, but only about 30% had manifest infectious mononucleosis. Lymphoproliferation and lymphoma were the major clinical manifestations (70% and 43%, respectively), and 9 of the CD27-deficient patients developed hemophagocytic lymphohistiocytosis. 21 patients (43%) developed autoinflammatory features such as uveitis, arthritis, and periodic fever (Ghosh S et al. 2020).