Acute suppurative thyroiditis caused by an infected piriform sinus fistula with thyrotoxicosis

We report herein an unusual case of thyrotoxicosis caused by acute suppurative thyroiditis (AST) infected through a piriform sinus fistula (PSF). A 28-year-old man presented with pain over the thyroid gland and elevated serum thyroid hormone levels, a picture similar to subacute thyroiditis. A fine-needle aspiration biopsy from the left lobe showed neutrophil infiltration, and culture from the aspirate grew anaerobic peptostreptococcus. A neck computed tomography (CT) scan showed an abscess in the thyroid gland, and barium swallow revealed the presence of PSF. Appropriate antibiotic treatment ameliorated his symptoms of infection, followed by normalization of thyroid function. Three months later, he underwent fistulectomy and partial left lobectomy. The end of the PSF track was found in the left thyroid lobe. Thus infection of the thyroid gland through the infected PSF was likely the cause of supprative thyroiditis. The unusual clinical features of AST in this patient include the presence of severe thyrotoxicosis, relatively late onset (28-years-old) of infection despite the presence of congenital PSF, and the lack of acute inflammatory signs on the overlying skin of the thyroid gland. It is important to recognize this type of AST, since fistulectomy is required to prevent recurrent AST.