Successful Use of Rituximab in a Case of Riedel Thyroiditis Resistant to Treatment with Prednisone and Tamoxifen

Abstract

Objective: Riedel thyroiditis (RT) is a rare disorder with high morbidity and limited treatment options. We describe a case resistant to conventional treatment with corticosteroids and tamoxifen, which subsequently responded to rituximab. Methods: Surgical pathology with hematoxylin and eosin staining was initially performed to confirm diagnosis, followed by IgG4 immunostaining and IgG4 serology in the setting of refractory RT, given its association with IgG4-related disease. Response to treatment was monitored subjectively as well as objectively with serial computed tomography scans. Results: A 51-year-old female with history of Hashimoto thyroiditis presented with compressive neck symptoms. Imaging was suggestive of a multinodular goiter with a large right thyroid nodule. Total thyroidectomy was planned, however intraoperative findings of a densely adherent thyroid with disruption of resection planes led to early termination of surgery. Biopsies obtained during surgery showed benign thyroid tissue with chronic lymphocytic thyroiditis, dense fibrous scar tissue, and benign lymph nodes, confirming the diagnosis of RT. The patient had minimal symptomatic improvement with chronic prednisone as high as 60 mg daily with tamoxifen at 30 mg twice a day. She subsequently received 4 doses of intravenous rituximab at 375 mg/m 2 every 3 weeks, resulting in significant subjective improvement of her compressive symptoms as well as an objective decrease in size of the thyroid mass as seen on a subsequent computed tomography scan. Conclusion: Evidence regarding etiology and management of RT is limited. We present a case of refractory RT treated with rituximab with resultant symptomatic improvement, thus providing further evidence for use of rituximab in resistant cases. (AACE Clinical Case Rep. 2019;5:e218-e221) Abbreviations: IgG4-RD = IgG4-related disease; RT = Riedel thyroiditis

Riedel’s Thyroiditis: Pitfalls in Diagnosis and Subsequent Complications

“…A drug gaining popularity in the treatment of refractory Riedel's thyroiditis is Rituximab, a monoclonal antibody against the CD20 protein found mainly on B lymphocytes. It is the therapy of choice after the failure of conventional therapies [ 17 ] and has been successful in several case reports [ 18 , 19 ]. Low-dose radiation therapy has also been used as a treatment option in cases of total refractory Riedel's thyroiditis, although its efficacy has not been established [ 5 ].…”

IgG4-related sclerosing thyroiditis (Riedel-Struma): a review of clinicopathological features and management

“…This has an anti-inflammatory effect and reduces the size of the gland, allowing the relief of compressive symptoms. Glucocorticosteroid therapy is effective but may be followed by relapses requiring the use of immunomodulatory agents, such as azathioprine, methotrexate, and recently rituximab [ 11 , 13 , 113 ]. In patients with symptomatic fibro-inflammatory disease in a hypothyroid phase, levothyroxine therapy should be started, and in special cases, anti-inflammatory drugs and vitamin D should be administered [ 4 , 77 , 93 , 116 – 118 ].…”

“…Currently, no acute overdose of tamoxifen has been observed [ 10 , 11 , 15 , 18 , 19 , 24 , 31 , 43 , 45 , 47 , 78 , 97 , 107 – 110 ]. It is noted that tamoxifen is used in other inflammatory conditions related to multifocal fibrosis [ 108 ].…”

Reidel’s Thyroiditis, a Diagnostic and Management Challenge: A Case Report and Review of the Literature

“…Mycophenolic acid, the active metabolite of mycophenolate, induces inhibition of T-and B-cell production, thus reducing the spread of antibody levels [13]. Rituximab has been reported to have favorable effects in IgG4-related systemic disorders and in some cases of RT [14]. As far as surgical management is considered, the indications are essentially two: sample for histopathological diagnostic confirmation and relieving compression or obstruction in the trachea or esophagus.…”