The patient has hyponatremia with a sodium (Na) level of 128 mmol/L, and the Coccidioides antibody titer level is high at 1: 32; otherwise, the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rapid plasma reagin (RPR), methylmalonic acid, human immunodeficiency virus (HIV)1/2, paraneoplastic profile, brucella immunoglobulin M (IgM), brucella immunoglobulin G (IgG), encephalitis antibodies (Abs), West Nile antibody immunoglobulin G (Ab IgG), and immunoglobulin M (IgM) are unremarkable. Here, CD40LG is linked to encephalitis.