Endocrine Abstracts

JOINT1006

Background: Riedl’s thyroiditis is a rare fibrosclerotic destructive thyroiditis of unknown etiology, arising either simultaneously or on preexisting autoimmune thyroiditis. We present a patient whose stable atrophic Hashimoto’s thyroiditis “transformed” to Riedl’s.

Case presentation: A 52-year-old woman with 3-year history of Hashimoto’s thyroiditis presented because of gradually increasing TSH from high-normal to a recent 10.1mIU/l. The patient complained of mild discomfort on palpation and on swallowing over the left cervical area, starting a month before. She had previously been euthyroid on a stable replacement dose of L-thyroxine 75 mg daily. Thyroid ultrasound had also been stable, showing a small, slightly hypoechoic gland with increased vascularity. Past medical history was unremarkable and family history for autoimmune diseases was negative. On examination, the thyroid gland was visibly enlarged, hard and slightly tender on palpation. Ultrasound imaging showed marked change with bilateral hypoechoic avascular areas, measuring 23x 15 mm and 16x 14 mm, with a rim of hypervascular thyroid parenchyma. TSH was 8.14mIU/l, thyroglobulin 0.09ng/ml, CRP 2 mg/l (0-8) and ESR 8 mm/1hr. The findings were not consistent with subacute thyroiditis and an ultrasound-guided FNA was performed, (2 passes with a 23G needle and one pass with a 21G needle), with complete absence of material for cytology. Subsequently a core biopsy was performed, with findings consistent with Hashimoto’s thyroiditis, while symptoms remained stable. A six-week trial of oral methylprednisolone had no effect. Finally, the decision was made to proceed to surgery due to diagnostic uncertainty and unremitting disease. The left lobe of the gland was removed piecemeal, without adverse events. The procedure was not completed because of significant risk of complications. Histopathologic diagnosis showed complete absence of follicles, diffuse fibrous tissue infiltrating parathyroid tissue and striated muscle, IgG4 positive plasmatocytic infiltrate and eosinophils, consistent with Riedl’s thyroiditis. The patient remains stable on follow-up without systemic manifestations.

Conclusion: The diagnosis of Riedl’s thyroiditis must be included in the differential diagnosis when a change in thyroid appearance or size associated with compressive symptoms occur in a patient with Hashimoto’s thyroiditis. Awareness of this condition is important for appropriate management.

References: 1. Endocrine (2018) 60:185–192.

2. J Clin Endocrinol Metab, October 2011, 96(10):3031–3041.