Hyper IgM Syndromes is an inherited as an X- linked syndrome. Most of the other forms are inherited as autosomal recessive traits, patients with Hyper-IgM (HIGM) syndrome are susceptible to recurrent and severe infections and in some types of HIGM syndrome there is an increased risk of cancer as well. The disease is characterized by decreased levels of immunoglobulin G (IgG) in the blood and normal or elevated levels of IgM. The most common form of HIGM syndrome is a defect or deficiency of a protein called CD40 ligand that is found on the surface of activated T-lymphocytes. The affected protein ligates, to a protein on B-lymphocytes called CD40 as the CD40 ligand is encrypted by a gene on the X-chromosome hence it is inherited as an X-linked recessive trait. As a consequence of the deficiency in CD40 ligand, the T-lymphocytes in the affected patients are unable to instruct B-lymphocytes to switch their production of immunoglobulins from IgM to IgG, IgA and IgE.