Riedel's goiter E06.5

Riedel's stroma, a rare, rind-like disease leading to chronic fibrous destruction of the thyroid gland, is an organ manifestation of IgG4-associated (autoimmunological) diseasesas an invasive sclerosing thyroiditis.

The incidence and prevalence of Riedel's goiter in the European population is unknown. In a larger collective, 191 cases of Hashimoto's thyroiditis were diagnosed with Riedel's thyroiditis 5 times (Jokisch F et al. 2016).

w>m; in a larger Danish collective the mean age at diagnosis was 50 years (25-81 years) (Falhammar H et al. 2018).

In the course of chronic, sclerosing inflammation, healthy thyroid tissue is gradually replaced by dense, fibrotic tissue. The remodeling is not limited to the "thyroid" organ. Invasion of adjacent tissues also occurs, resulting in the typical clinic of non-swallowable, baked goiter ("iron-hard goiter"). It can lead to tracheal narrowing and even recurrent paresis (Chong Xi R et al. 2016). This can mimic thyroid carcinoma, especially since there may be concomitant regional IgG4-associated (painless) lymphadenopathy ( Sakai et al. 2018).

Patients usually present with a euthyroid metabolic state at onset, but this can lead to a hypothyroid situation with increasing destruction of healthy thyroid tissue.

In isolated cases, Riedel's stroma may be associated with mediastinal and/0r subcutaneous (fasciitis) fibrosis (Abulafia J et al 1967).

The IgG4 serum level may be elevated.

Chronic fibrosing thyroiditis, rich in plasma cells. No significant tissue sesophilia is observed. Significantly increased IgG4/IgG ratio. The histological picture differs only gradually from the fibrous variant of Hashimoto's thyroiditis.

Characteristic clinic; sonographic evidence of fibrotic remodelling of the tissue and potential infiltration of adjacent tissue and organs. A biopsy can histologically confirm the final diagnosis

First-line therapy (as in other IgG4-associated diseases) consists of systemic glucocorticoids. Among these, rapid response. In individual cases, tamoxifen and rituximab have been used in cases of steroid resistance. Surgical debulking is the option in case of insufficient drug response (Kottahachchi D et al. 2016).

The fibrosing subtype of Hashimoto's thyroiditis is now also classified as IgG4-associated disease.

1. Abulafia J et al. (1967) Subcutaneous idiopathic fribomatosis(fascitis type). Combined with idiopathic mediastinal fibrosis and Riedel's struma (analysis of a general classification of fibromatous hyperplasias). Arch Argent Dermatol 17:1-20.

2. Bledsoe JR et al (2018) IgG4-related disease: review of the histopathologic features, differential diagnosis, and therapeutic approach. APMIS 126:459 476.
3. Chong Xi R et al (2016) Severe tracheal compression caused by Riedel's thyroiditis: A case report and review of the literature. Ann Med Surg (Lond) 12:18-20.
4. Falhammar H et al (2018) Riedel's thyroiditis: clinical presentation, treatment and outcomes. Endocrine 60:185-192.
5. Jokisch F et al. (2016) A small subgroup of Hashimoto's thyroiditis is associated with IgG4-related disease. Virchows Arch 468:321-327.
6. Kottahachchi D et al (2016) Immunoglobulin G4-Related Thyroid Diseases. Eur Thyroid J 5:231-239.
7. Sakai Y et al (2018) Case report: IgG4-related mass-forming thyroiditis accompanied by regional lymphadenopathy. Diagn Pathol 13:3.