Background: Since the beginning of the pandemic we have learned much about acute organ complications due to COVID-19, but we are still only beginning to understand the post-infection complications.
Case presentation: A man in his forties was diagnosed with subacute thyroiditis after a mild COVID-19 infection. This is an important differential diagnosis to consider if after a period of improvement, an infected patient develops fever, pain around the region of the thyroid (throat/neck) and/or symptoms of hyperthyroidism.
Interpretation: Subacute thyroiditis is thought to be initiated by a viral infection or postviral inflammatory process, often in patients with a history of an upper respiratory infection typically two to eight weeks prior to the onset of thyroiditis. The condition is believed to be triggered by an antigen created by the virus. Subacute thyroiditis must be on the list of possible differential diagnoses in patients with COVID-19 whose condition deteriorates after a period of improvement.