Lambda 5 Deficiency is related to mu chain disease and congenital hypogammaglobulinemia. An important gene associated with Lambda 5 Deficiency is IGLL1 (Immunoglobulin Lambda Like Polypeptide 1), and among its related pathways/superpathways are Class I MHC mediated antigen processing and presentation and Prolactin Signaling. Related phenotypes are Synthetic lethal with vaccinia virus (VACV) infection and immune system