Hyper IgM Syndrome Type 2 is a rare disease.Unlike other hyper-IgM syndromes, the Type 2 patients identified thus far did not present with a history of opportunistic infections. One would expect opportunistic infections in any immunodeficiency syndrome. The putative genetic lesion is in the AICDA gene found at 12p13. The patients have three common findings:
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.