While CVID can develop later in life and its causes are thought to be multifactorial (9), XLA is a congenital disease that is the result of a mutation in Bruton's tyrosine kinase, resulting in an early B cell defect and complete humoral immunodeficiency from birth, including IgG, IgA and IgM (12). Here, CD40LG is linked to common variable immunodeficiency.