The hyper-immunoglobulin M syndromes (HIGM) are a heterogeneous group of genetic disorders, due to several mutations of activation-induced cytidine deaminase (AICDA) inducing extremely elevated IgM and significantly decreased IgG and IgA, which has been rarely reported to be associated with GHD [56]. This evidence concerns the gene AICDA and hyper-IgM syndrome.