On admission, laboratory studies showed a normal white blood cell count with a normal differential count. His hemoglobin level was 8.7 g/dL (to convert to grams per liter, multiply by 10), with a mean corpuscular volume of 88.2 μm3 (to convert to femtoliters, multiply by 1.0). He had a platelet count of 196 × 103/μL (to convert to ×109/L, multiply by 1.0), a lactate dehydrogenase level of 312 U/L (to convert to microkatals per liter, multiply by 0.0167), an erythrocyte sedimentation rate of 120 mm/h, and a C-reactive protein level of 8.8 mg/L (to convert to nanomoles per liter, multiply by 9.524). The results of renal and liver function tests, including coagulation studies, were normal. His lipid profile was unremarkable. His vitamin B12, folic acid, thyrotropin, and ammonia levels were normal. The results of hepatitis A, B, and C and human immunodeficiency virus serologies were negative. The results of West Nile virus, Epstein-Barr virus, and Lyme disease serologies were negative. Anti-La, anti-Ro, antiphospholipid, anticardiolipin, and anti-Purkinje cell antibodies were negative. Thyroid peroxidase antibody titer was elevated at 73.5 U/mL. Serum immunofixation revealed no monoclonal gammopathy. Blood and urine culture results were negative.