Recurrent Subacute Thyroiditis Lacking Diagnostic Imaging Features: Atypical Scenario

ABSTRACT Objective: A diagnosis of subacute thyroiditis (SAT) is based on history and clinical features supported by laboratory investigations and imaging studies. However, the presence of SAT with normal thyroid scintigraphy findings is exceedingly rare. Methods: We report the history, exam findings, laboratory results, and imaging studies of a 51-year-old postmenopausal female with SAT. Results: The patient had a history of recurrent SAT 10 years back and presented now with pain in her neck for 1.5 months, fever for 3 days, heat intolerance, sleep disturbances, and restlessness. Physical examination revealed enlargement and marked tenderness over the thyroid. Thyroid profile showed thyroid-stimulating hormone (TSH) 0.023 μIU/mL (normal, 0.4 to 4.2 μIU/mL), free thyroxine (FT4) 2.31 ng/dL (normal, 0.89 to 1.76 ng/dL), and free triiodothyronine (FT3) 2.74 ng/dL (normal, 1.3 to 3.1 ng/dL). Tc-99m pertechnetate scintigraphy showed bilateral normal homogenous uptake in both lobes of the thyroid. Patient was started on 1 tablet carbimazole 5 mg three times daily, but she returned 2 weeks later with persistence of symptoms. Repeat labs showed TSH, 0.008 μIU/mL; FT4, 2.64 ng/dL; and FT3, 2.5 ng/dL, with erythrocyte sedimentation rate (ESR) of 94 mm/hour (normal, 0 to 20 mm/hour). Carbimazole was stopped and prednisolone was started in tapering doses for 6 weeks. Improvement in symptoms with normalization of ESR to 8 mm/hour and FT4 to 1.04 ng/dL occurred after taking prednisolone for 6 weeks at follow-up. Conclusion: This patient presenting with typical clinical features of SAT and elevated ESR but lacking the characteristic imaging thus emphasizes diagnosis of SAT on the basis of history, physical examination, and laboratory data, even if thyroid scintigraphy findings are not in favor of disease. Abbreviations: ESR = erythrocyte sedimentation rate; FT4 = free thyroxine; SAT = subacute thyroiditis; TSH = thyroidstimulating hormone