Mondo Description A form of Hyper IgM syndrome characterized by mutations of the CD40 gene. In this type, Immature B cells cannot receive signal 2 from helper T cells which is necessary to mature into mature B cells.

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.