Endocrine Abstracts

Background: Subacute thyroiditis (SAT) is a transient inflammatory, probably viral disease of the thyroid gland. It is clinically characterized by pain, fever, increased erythyrocyte sedimentation rate (ESR) or other markers of inflammation, transient thyrotoxicosis, and has a tendency to recur. In most cases, in addition to the clinical features, scintigraphy and ultrasound may support the diagnosis of SAT. However, in the present case, SAT with an atypical thyroid ^99mTc uptake and a nodule formation in ultrasound lead to diagnosis difficulties.

Case presentation: A 31-year-old woman with the clinical suspicion of SAT was observed. Thyrotoxicosis was present and the tests for anti-thyroid peroxidase, anti-thyroglobulin and TSH receptor antibodies were negative. Thyroid scintigraphy with ^99mTc demonstrated decreased uptake in the right but a normal uptake in the left lobe. Four weeks after clinical and laboratory remission she developed a painful palpable nodule of the left thyroid lobe. Increased erythyrocyte sedimentation rate above 100 mm/h and elevated C reactive protein were present. Ultrasonographic examination showed an enlarged left lobe and area of low echogenicity with shaded margins and microcalcifications. The lesion showed a contrast uptake in contrast-enhanced magnetic resonance imaging (MRI). The second scintigraphy demonstrated a bilateral, heterogeneous uptake with a suspected hipoactive nodular image of the left thyroid lobe. Fine-needle aspiration biopsy from the nodule revealed multinuclear giant cells consistent with SAT.

Conclusion: In most cases, the diagnosis of SAT can be made based on the physical and laboratory findings of the patient and the clinical course of the disease. Findings of thyroid scintigraphy and ultrasound that are not consistent with subacute thyroiditis do not exclude the diagnosis of SAT. For definitive diagnosis of an atypical SAT and exclusion of thyroid malignancies, fine-needle aspiration biopsy may be required.