Endocrine Abstracts

Introduction: Riedel thyroiditis is a rare form of infiltrative and fibrotic disease of the thyroid which may involve neighbouring tissues. The main differential diagnosis of Riedel thyroiditis includes malignant tumors and fibrosing Hashimoto’s thyroiditis.

Herein, we report a case of concurrent Riedel’s disease and Hashimoto’s thyroiditis.

Observation: A 45-year-old woman was diagnosed with goiter and hypothyroidism. She was treated with Levothyroxine. Two months later, the patient presented with a rapidly growing goiter associated with dysphagia for solids and dyspnoea.

Physical examination revealed a hypothyroid state, a large and hard goiter.

Thyroid functions tests showed a TSH of 59.07 μIU/ml and a FT4 of 0.83 ng/dl. The antibody tests were performed, revealing positive thyroperoxidase antibodies of 386.8 IU/ml (NR: <35 ui/ml) and thyroglobulin antibodies >5000 IU/ml (NR: <225 IU/ml).

Cervical ultrasonography revealed an enlarged heterogeneous thyroid gland (right lobe: 66 × 37.5 × 32.5 mm, left lobe: 61 × 42 × 38 mm) with no evidence of nodular lesions. Ct-scan revealed a hypodense thyroid gland hypertrophy extending to adjacent tissues.

The Levothyroxine dose was increased and the patient was referred for total thyroidectomy.

However, thyroidectomy couldn’t be performed due to hard adhesion to neighboring structures. Analysis of surgical biopsy section revealed fragments of fibrous tissue with diffuse inflammatory infiltrate composed of lymphocytes, plasma cells and eosinophils. Fibrosis and inflammation infiltrated muscle and adipose tissues around the thyroid gland. There were no evidences of malignancy.

Considering the clinical course and histopathological findings, the diagnosis of Riedel’s goiter with coexistent Hashimoto’s thyroiditis was established.

High dose of corticosteroids was successfully used in our patient.

Conclusion: It’s difficult to differentiate between Riedel’s thyroiditis and fibrosing Hashimoto’s thyroiditis. However the coexisting of both diseases has been reported in few cases and seems to be coincidental.