For this culture-negative PJI, serological analysis was conducted in the bacteriology laboratory of Lyon Hospital (Immunofluorescence assay, Focus diagnostics, Cypress, USA) for Q fever and revealed significant titers (phase I; IgG 1:2048 [cut-off limit of positivity, 256] without IgM or IgA; phase II: IgG 1:512 without IgM or IgA) (Fig. 2). Here, CD40LG is linked to Fever.