A 48-year-old man with history of recent travel to central Mexico and immunosuppression sought treatment with a 1-month-long history of progressive headache, fatigue, word-finding difficulties, and night sweats. The patient had a history of end-stage renal disease; he had undergone a kidney transplantation 7 years prior with good graft function with immunosuppression with tacrolimus, everolimus, and low-dose prednisone. At an outside hospital, he recently had been treated with empiric antibiotics for meningitis, but these were discontinued given the low suspicion for a bacterial cause. After discharge, he continued to have headaches, limited oral intake, persistent nausea, urinary frequency, and falls, prompting him to seek treatment at the ED. Physical examination findings were benign aside from disorientation. Laboratory workup was significant for hyponatremia of 122 mM, creatinine of 1.4 mg/dL (baseline, 1.4-1.5 mg/dL), WBC count of 7.2 109/L, hemoglobin of 13 g/dL, and platelet count of 349 109/L. Neither tacrolimus nor everolimus levels were supratherapeutic.