Steroid responsiveness in a case of Riedel's thyroiditis and retroperitoneal fibrosis.

Riedel's thyroiditis is a rare chronic inflammatory disease of the thyroid characterised by an invasive fibrotic process. We present a lady with newly diagnosed hypothyroidism, rapidly enlarging hard, fixed goitre, strongly positive thyroid antibodies and raised erythrocyte sedimentation rate (ESR). A tru-cut biopsy confirmed Riedel's struma. Regression of the goitre and reduction of antibody titres occurred after starting prednisolone, which was stopped after 10 months. Six months later, she presented with renal failure due to retroperitoneal fibrosis that was successfully treated by reinstitution of steroids and ureteric stenting. Very high titres of thyroid antibodies and hypothyroidism predating development of goitre suggest coexistence of Hashimoto's thyroiditis and Riedel's thyroiditis. Tru-cut biopsy obviated the need for open thyroidectomy. A predominantly inflammatory as opposed to fibrotic thyroid histology may predict good response to steroids. Relapse following steroid withdrawal may not only be in the thyroid but also at other sites.