A repeat IgM and IgG Lyme immunoblot January 2019 revealed decreased Borrelia-specific bands over time (23 kDa [OspC], 39 kDa) but a Bartonella IgM Western Blot was performed for resistant symptoms (despite negative local testing) and returned indeterminate positive with exposure to Bartonella vinsonii sub-species, with a Bartonella FISH turning positive, confirming an active Bartonella infection. Here, CD40LG is linked to bartonellosis.