A 42-year-old woman presented with a rapidly enlarging right-sided thyroid mass and underwent hemithyroidectomy. Riedel's
thyroiditis was only diagnosed upon
surgical decompression of the right carotid artery 2 years later. She became more symptomatic as Riedel's
thyroiditis progressed, and mediastinal fibrosclerosis developed over the next 12 months. Oral
prednisolone failed to improve her condition, and she was commenced on
tamoxifen. Despite initial improvement, her symptoms recurred 2 years later, mainly arising from compression of the trachea and esophagus at the thoracic inlet. Fluorodeoxyglucose positron emission tomographic scan showed locally advanced active invasive fibrosclerosis in the neck and mediastinum. An elevated
activin-A level of 218 pg/mL was consistent with active
inflammation.
IgG subtypes (including
IgG4) were normal. Two courses of iv
methylprednisolone were given but only produced transient improvement. Subsequently, the patient received 3 doses of i.v.
rituximab at monthly intervals and had prompt sustained symptomatic improvement.
Activin-A level decreased to 122 pg/mL 10 months after
rituximab therapy. Fluorodeoxyglucose positron emission tomographic scan 6 weeks after
therapy showed reduction in
inflammation. A further scan
at 10 months demonstrated ongoing response to
rituximab. This is a case of refractory Riedel's
thyroiditis with symptomatic, biochemical, and radiological improvement that has persisted 14 months after
rituximab. The likelihood and duration of response to
rituximab in Riedel's
thyroiditis requires further study.