(15.15) Thyroid Nodule, Cyst, or Abscess?

Thyroid abscesses are rare due to protective mechanisms inherent to the thyroid gland such as vascularity, encapsulation, and iodine content. Thyroid abscess accounts for less than 1% of thyroid diseases and can be easily missed. We present a case of a thyroid abscess secondary to Escherichia coli (E. coli) that occurred a few months after subacute thyroiditis. 

Case(s) Description :

A 74-year-old male with hypertension, hyperlipidemia, and coronary artery disease was hospitalized for weakness, night sweats and weight loss attributed to Epstein-Barr Virus (EBV). He denied toxic habits or history of thyroid illness, nodules, iodine contrast or radiation exposure. His TSH was 0.78 (0.340 – 4.820 uIU/ml) and free T4 1.86 (0.59 – 1.80 ng/dl) and he was started on methimazole 2.5 mg daily. 

A thyroid ultrasound in the hospital showed a right-sided solid, hyperechoic 2.6 cm nodule and midline complex solid cystic nodule, measuring up to 6.8 cm. CT scan of neck showed mild tracheal deviation.

One month after hospitalization, he had laboratory tests that showed TSH of 0.11 mIU/L (0.40 – 4.50 mIU/L) with free T4 1.0 (0.59 – 1.80 ng/dl) and free T3 3.5 (2.3-4.5 pg/mL). Thyroid peroxidase antibodies were elevated at 463 IU/mL (normal < 9 IU/mL) and thyroid stimulating immunoglobulin was normal. His thyromegaly improved and methimazole was discontinued. A thyroid uptake was 4.9% (reference range 5-18%), suggesting thyroiditis.

Three months later, he experienced swelling and tenderness in his neck. Repeat test for TSH, free T4 and total T3 all returned within normal limits.  One week later, he was admitted to the hospital for purulent drainage on his anterior neck, accompanied by swelling, redness and warmth. He had leukocytosis (WBC count 12.4 K/uL, 4-10.5 K/uL). A CT scan of the neck revealed soft tissue edema and stranding. He was diagnosed with sepsis secondary to anterior neck cellulitis and thyroid abscess. He underwent incision and drainage of the abscess, and the wound culture confirmed infection with E. coli. Treatment involved intravenous piperacillin-tazobactam and vancomycin, transitioned to levofloxacin upon discharge. Further testing revealed positive EBV and cytomegalovirus IgG with negative tests for HIV and hepatitis. 

Discussion :

Thyroid abscess is a rare condition that can be difficult to diagnose. It should be considered in patients with a history of thyroid illness, neck swelling, tenderness, and fever. Thyroid ultrasound is the preferred imaging modality due to its widespread availability. It frequently reveals a heterogenous thyroid gland adjacent to or overlapping an anechoic or hypoechoic mass. Clinicians should be able to identify both symptoms and ultrasounds findings associated with this condition.