Endocrine Abstracts

Infected thyroid cysts are a rare complication of the thyroid gland, with haematogenous spread from a distal site of infection believed to be one mechanism of infection. We report the case of a patient who presented with an infected thyroid cyst due to Capnocytophaga canimorsus bacteraemia after sustaining a dog bite on her hand. A 37-year-old female presented to the Emergency Department with a five-day history of fevers, neck pain, and a rapidly enlarging neck swelling. The patient reported a dog bite on her right hand two days prior. Physical examination revealed temperature of 39.2°C, tachycardia, and a 3 cm tender mass in the left thyroid lobe. Laboratory investigations demonstrated leukocytosis (white blood cell count: 16.6×10⁹/l) and elevated C-reactive protein (160 m g/l). Thyroid Ultrasound revealed a 3.1 cm left lobe cyst which demonstrated vascularity, and an overall multinodular appearance to the left lobe. The thyroid cyst was aspirated, and the fluid culture grew gram negative bacillus. Subsequent PCR testing confirmed this as Capnocytophaga canimorsus. The infected thyroid cyst was attributed to haematogenous spread of bacteria. Following a two week course of ceftriaxone and metronidazole, the patient’s condition improved, with resolution of fever and normalisation of inflammatory markers. Capnocytophaga canimorsus is a gram-negative bacterium and an oral commensal in dogs, and occasionally causes serious infections in humans. To our knowledge, this is the first case report of an infected thyroid cyst due to capnocytophaga canimorsus.