Riedel’s thyroiditis is rare inflammatory disorder of the thyroid gland characterised by extensive fibrosis of the gland and progressive invasion to the surrounding structures.1 The earliest cases were reported by Bernhad Riedel in 1896.4 It usually presents with a hard goitre, which may be difficult to differentiate from malignancy. The thyroid function is mostly euthyroid, but sometimes it can be hypothyroid and in addition there may be hypoparathyroidism which could be due to extensive fibrosis. In severe cases it give rise to stridor, dyspnoea, dysphagia.5 The management may involve both surgical and medical treatment.

A 48 year old female presented to the ENT clinic with stridor, dyspnoea and anterior neck swelling. Examination revealed an asymmetrical goitre with an enlarged, hard, irregular fixed left lobe suggestive of neoplasm. Blood tests including scrum T4, TSH & calcium were all within normal limits. Anti TPO antibodies were not detected. CRP and ESR were mildly elevated. Fine needle aspiration was inconclusive. An urgent CT scan showed a large thyroid mass with focal calcification, largely involving the left lobe encasing the trachea with moderate tracheal stenosis.(Fig 1)

She underwent open exploration of the thyroid and frozen section biopsy. Results suggested Reidel’s Thyroiditis.(Fig 2)

She was treated initially with high dose steroids (80mgs Prednisolone), which led to a regression of goitre, improvement in flow volume loop and normalisation of ESR & CRP over the course of several weeks. The dose of prednisolone was gradually reduced to 5mg daily and her symptoms remained controlled. The right lobe of thyroid became impalpable and she was left with a small hard nodule in the left lobe.  After 18 months the patient had a recurrence of stridor associated with hard irregular enlargement of both thyroid lobes. Inflammatory markers remained suppressed and she made a partial improvement of goitre on high dose prednisolone (80mg daily initially) with persistence of stridor. At this stage she was started on tamoxifen 20mg daily addition to prednisolone and had a slow improvement in her stridor over next six months. She has now remained stable on tamoxifen with normal flow volume loops for one year.

The aetiology of Riedel’s thyroiditis is unknown.4 Many theories having been proposed for the pathogenesis. The extensive infiltration of mononuclear and eosinophils supports an immune-mediated process, as does the detection of thyroid specific autoantibodies in a large proportion of patients. In one series autoantibodies were found in 67% of cases.2  It was previously proposed that Riedel’s thyroiditis represented a late form or variant of Hashimotos or DeQuervains thyroiditis, although this is no longer thought to be true.3 Riedel’s thyroiditis is a rare disorder. The largest series from the Mayo clinic in 1957 reported twenty cases from 42,000 thyroidectomies performed over a period of 35 years.4

Classically the presentation is a stony hard thyroid mass, which may be adherent to surrounding structures and difficult to differentiate from malignancy.7 It may present with compressive symptoms such as stridor, dyspnoea, dysphagia.5,7 There is an association with fibrosis of other organs includes lung, liver, bile duct and retroperitoneal tissues.11 These manifestations usually occur years after initial presentation with Riedel’s thyroiditis, supporting the concept that it may be part of idiopathic fibrosclerosis, a generalised disorder.6

Most cases involve both thyroid lobes and patient are typically euthyroid.3 Hypothyroidism is found in only 0.25% of cases, usually associated with complete thyroid involvement.7 Development of hypoparathyroidism is extremely rare, again due to extensive fibrosis.8

Surgery may be required to release the trachea and to perform open biopsy,1 although some advocate thyroid lobectomy for unilateral disease.4 Rarely emergency tracheostomy is required for the patients with severe stridor.

Medical therapy with high dose corticosteroid has traditionally been the treatment of choice,2,10,12,13,14 although there are no randomised controlled trials. Some patients will get long term benefit following steroid withdrawa1,2,14 while others may suffer relapse following steroid withdrawal,13 as in the case described. Some patients do not respond to steroid treatment, usually due to a longer duration of disease.14 Rarely spontaneous remission can occur as shown in the case report by Hartemann.15

In those who fail to respond to, or relapse on corticosteroid, the only effective agent is tamoxifen. Experience to date with this agent is limited, but Few et al described responses to tamoxifen in a small series of four patients with steroid resistant Riedel’s thyroiditis.9 The putative mode of action for tamoxifen is thought to be inhibition of fibroblast proliferation through the stimulation of release of transforming growth factor-beta.9

References

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