Hyper IgM syndrome

Hyper IgM syndrome is a group of rare primary immune deficiency disorders. They are characterized by low or absent levels of the serum antibodies IgG, IgA and IgE alongside normal or raised levels of IgM. The underlying problem lies in the pathway running from B-cell activation to isotype class switching, which is why the group is also known as the immunoglobulin class switch recombination deficiencies. Patients are usually diagnosed within the first two years of life and experience severe immunosuppression. The most common cause is a mutation in the CD40 ligand gene, CD40LG, located at Xq26.3-27, which produces the X-linked form of the syndrome in males.