A 2-month-old male was admitted to the hospital because of 2 consecutive days of fever. On admission, the infant was febrile with normal skin turgor. Lung, heart, and abdomen were unremarkable at examination, and the only outstanding sign was a generalized macular rash on his trunk.Laboratory exams showed a white blood cell count (WBC) of 10,300/mm 3 , with 58.8% neutrophils, 27% lymphocytes, and 5.7% monocytes; 10.1 g/dL of hemoglobin; and an elevated level of C-reactive protein (CRP, 18.6 mg/dL).Urine analysis revealed pyuria (183 WBC/mcL). Sepsis related to a urinary tract infection was presumed, and intravenous ampicillin and gentamicin were started.Abdominal ultrasound and echocardiography were performed and revealed normal findings. Fever persisted on the third day in the hospital despite antibiotic therapy, and the overall condition of the patient became worse.Nonpurulent bulbar conjunctivitis appeared. Due to his fever, poor appetite, irritability, and signs of meningismus and opisthotonus, a lumbar puncture was performed after a magnetic resonance imaging (MRI) exam of the head was negative.Cerebrospinal fluid (CSF) examination showed mildly elevated protein level (63.2 mg/dL) with normal glucose concentration and no cells. His blood, CSF, urine, and stool cultures were negative. Virologic tests (human herpesvirus 6, cytomegalovirus, herpes simplex viruses 1 and 2, enterovirus, and Epstein-Barr virus) were all negative by polymerase chain reaction.Laboratory investigations showed an increment of inflammatory markers (CRP 27.1 mg/dL; fibrinogen 600 mg/ dL) and leukocytosis (31,100/mcL).On the fourth day, thrombocytosis (platelets 696,000/mcL) was detected. On the fifth day of admission, a lab test was performed and revealed the diagnosis.