CD40LG and infectious disease: Due to the unknown cause of MFS, the infectious disease specialist recommended obtaining additional serum IgG and IgM West Nile, cytomegalovirus polymerase chain reaction (PCR), human immunodeficiency virus antibody, Epstein-Barr virus IgG and IgM serology, acute tick panel test, arbovirus panel test, Rickettsia typhi antibody, and gastroenterology pathogen panel.