A hyper-IgM syndrome characterized by the absence of immunoglobulin class switch recombination, the lack of immunoglobulin somatic hypermutations, and lymph node hyperplasia caused by the presence of giant germinal centers. The disease is hyper-IgM syndrome type 2 (MONDO_0011528). Also known as: AICDA hyper-IgM syndrome, Activation-induced cytidine deaminase deficiency, HIGM2, activation-induced cytidine deaminase deficiency, aid deficiency, hyper-IgM syndrome caused by mutation in AICDA.