What is Hyper-IgM syndrome?
Hyper-IgM syndrome, or ‘Hypogammaglobulinemia with Hyper-IgM’ is one of the rarer inherited immunodeficiencies. It is difficult to estimate the actual number of affected individuals as there are almost certainly a number of undiagnosed cases. However, an European database dedicated to the most well understood form of the Hyper-IgM syndrome now exists and contains data from 130 families. There are two types of Hyper-IgM syndrome, X-linked and Autosomal Recessive. • X-linked Hyper-IgM syndrome (XHIM) is the more common type and affects only males. ‘Carrier’ females have one copy of the abnormal gene on one of their two X chromosomes, but are themselves not affected. Sons of carriers have a 50% risk of inheriting the abnormal gene from their mothers. As males have only one X chromosome, if they inherit the abnormal gene they will be affected by the disease. Daughters of carriers have a 50% risk of being carriers. Approximately 30% of cases of XHIM arise as ‘new mutations’ and in these cas
