She remained serologically negative to leptospirosis, syphilis, and Lyme-disease–causing spirochetes using commercially available diagnostic tests (Leptospira immunoglobulin G [IgG] immunoglobulin M [IgM] ELISA test [Diagnostic Automation, Woodland Hills, CA, USA], Bioelisa Syphilis 3.0 test [Biokit, Lliçà d'Amunt, Spain], and Lyme Disease IgG/IgM ELISA kit [Diagnostic Automation]). Here, CD40LG is linked to leptospirosis.