Atypical Presentation of Riedel's Thyroiditis: Multifocal Nodular Fibrosis and Resolution with Levothyroxine.

Background: Riedel’s thyroiditis is characterised by chronic inflammatory invasive fibrosclerosis of the thyroid gland, surrounding structures, and extrathyroidal fibrosis. We present a case of Riedel’s thyroiditis associated with nodular fibrosis of the lungs and liver. Case: A 40-year-old woman presented with a 3-month history of neck swelling, difficulty swallowing and breathlessness on exertion. Core biopsy of the goitre revealed dense fibrous tissue with mixed chronic inflammatory cells. A staging computed tomography scan revealed a large thyroid mass encasing the oesophagus and compressing the trachea, multiple bilateral pulmonary nodules with no evidence of lymphadenopathy, and multiple suspicious nodular lesions in the liver. A thorascopic biopsy of a lung lesion in its entirety revealed a hyalinising lung lesion with no evidence of malignancy. Following the introduction of levothyroxine replacement, symptomatic improvement occurred in parallel with improvements in imaging. Conclusion: To our knowledge, this is the first description of Riedel’s thyroiditis presenting with nodular extrathyroidal fibrosis, and which showed resolution following institution of levothyroxine.