Painful Granulomatous Hashimoto Thyroiditis Uncovered Systemic Histoplasmosis

Background. Granulomatous thyroiditis is usually viral and very rarely due to fungal infection. Fungal thyroiditis affects the severely immunocompromised and only rarely immunocompetent individuals. Case report. A 32-year-old man with known Hashimoto thyroiditis was consulted for a 1-week history of neck pain, dysphagia, cough, asthenia, loss of appetite, and night sweats. Imaging showed an enlarged right thyroid lobe. Laboratory studies confirmed hypothyroidism. He underwent a thyroid lobectomy. Microscopic examination showed granulomas in a background of Hashimoto thyroiditis. Silver stain revealed numerous yeasts consistent with Histoplasma. Subsequent serology was also positive. Further evaluations were negative for acquired or constitutional immunodeficiencies. He was started on oral itraconazole with resolution of all constitutional symptoms. Conclusions. We report a second case of concurrent Hashimoto and Histoplasma thyroiditis in an immunocompetent patient. Systemic manifestations of fungal infection are confounded by systemic symptoms of thyroid dysfunction. Fungal thyroiditis is a manifestation of systemic fungal infection requiring prolonged systemic therapy to prevent complications or fatal outcomes.