Mondo Description 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.

Uniprot Description A rare immunodeficiency syndrome characterized by normal or elevated serum IgM levels with absence of IgG, IgA, and IgE. It results in a profound susceptibility to bacterial infections.