CD40LG and systemic lupus erythematosus: In our case, we explained that the result of the Coombs test was likely a false positive given evidence of normal serum levels of IgA, IgM, and IgE (IgG was not considered given he had received IVIG), and the lack of evidence for autoimmune hemolysis, lack of exposure to penicillin or cephalosporins, and absence of autoimmune conditions such as lupus.