A 45-year-old woman presented to our clinic in July 2019 for evaluation of intermittent fever, rigors, diaphoresis, malaise, and urinary symptoms of frequency and urgency of 5 days’ duration. Her history was notable for Graves disease after total thyroidectomy 8 months previously after failed medical management, with no neck swelling or pain at present; an incidentally discovered and resected papillary thyroid microcarcinoma; and hypertension. A reconciled medication list included levothyroxine (125 μg/d), sertraline (100 mg/d), amphetamine-dextroamphetamine (20 mg/d), propranolol (40 mg twice daily), selenium (200 μg/d), and biotin (10 mg/d). She reported no relevant family history or sick contacts, but she may have had tick exposure. Physical examination revealed a temperature of 39.4 °C, heart rate of 64 beats/min, blood pressure of 98/56 mm Hg, weight of 85 kg, exophthalmos and lagophthalmos, and healed Kocher incision with no neck masses or tenderness. Abdominal examination revealed mild suprapubic tenderness.
The differential diagnosis included infection (urinary tract infection [UTI], viral syndrome, tick-borne illness) and hyperthyroidism in the setting of ongoing levothyroxine therapy and her history of Graves disease. Subsequent laboratory studies revealed the following (reference ranges provided parenthetically): hemoglobin, 10.7 g/dL (11.6 to 15.0 g/dL); white blood cell count, 16.7 × 109/L (3.4 to 9.6 × 109/L); creatinine, 0.91 mg/dL (0.59 to 1.04 mg/dL); 2 sets of blood cultures with negative results; urine culture growing Escherichia coli, greater than 100,000 colony-forming units per milliliter; and negative results on a tick-borne pathogen panel including Lyme disease serology. Chest radiography revealed no abnormalities. Thyroid function testing (TFT) revealed the following: thyrotropin, 0.01 mIU/L (0.3 to 4.2 mIU/L); free thyroxine (fT4), 1.3 ng/dL (0.9 to 1.7 ng/dL); and free triiodothyronine (fT3) 2.4 pg/mL (2.8 to 4.4 pg/mL).
Antimicrobial therapy was initiated for a UTI.