A case of nontuberculous mycobacteria-associated thyroiditis mimicking subacute thyroiditis.

We describe a case of nontuberculous mycobacteria infection in the thyroid gland in a 54-year-old woman who had painful thyroid enlargement. Ultrasonography showed ill-defined hypoechoic lesions without increased vascularity in both upper lobes of the thyroid gland. Fine needle aspiration biopsy was performed, and pathology showed granulomatous inflammation with necrotic debris that the pathologist suspected was subacute granulomatous thyroiditis or tuberculosis of the thyroid gland. Nontuberculous mycobacteria infection was confirmed after right hemithyroidectomy. Antimycobacterial therapy was initiated as the treatment of choice. Nontuberculous mycobacteria in the thyroid gland appear to be rare. In clinical practice, however, it should be considered as a differential diagnosis of a painful thyroid mass. For accurate diagnosis, clinical and radiological features plus histological examination are required.