CD40LG and diphtheria: The presently described patient has normal for age IgG, and IgM, decreased IgA levels, normal distribution of IgG subclasses, low antigen-specific anti-tetanus and anti-diphtheria antibodies, accompanied by lymphopenia and aberrant B and T lymph cell, primarily T helper cell development that might be underpinning the proneness to infections and immune dysregulation.