Riedel thyroiditis is a visceral fibromatosis characterized by the replacement of the functional tissue of the thyroid parenchyma with connective tissue. Fibrosis often spreads to the neurovascular bundle of the neck, trachea and esophagus. Patients are concerned about discomfort in the throat area – compression, a feeling of a coma or a foreign body, which increases during swallowing. In the later stages, the mobility of the tongue and adam’s apple is limited. CT and ultrasound of the thyroid gland, fine needle aspiration biopsy of nodes are used to establish the diagnosis. Surgical treatment – isthmus resection, hemithyroidectomy, thyroidectomy.
In the second half of the XIX century, the German surgeon B. Riedel was the first to describe a form of thyroiditis, in which goiter is formed as a result of the gradual growth of connective tissue. Synonymous names of Riedel thyroiditis are fibrous thyroiditis, fibroinvasive goiter. Pathology has a chronic course, it is diagnosed very rarely. It accounts for 0.05% of cases of all thyroid diseases. The prevalence among operated patients is 0.01%. The diagnosis of fibrotic thyroiditis can be confirmed in people of any age, but the incidence increases between 35-60 years. Pathology is noticeably more common in women.
Currently, there is no single point of view on the factors that provoke the formation and growth of fibroinvasive goiter. Some researchers suggest that Riedel thyroiditis is of autoimmune origin and represents the final stage of Hashimoto’s disease. However, it is not possible to confirm this assumption, since antibodies are not detected in the blood plasma of patients. According to another theory, fibromatous thyroiditis is a specific stage of subacute thyroiditis. But there is no information objectively confirming the transition of the granulomatous form to the fibrous one.
Viral infection is considered as the most likely provoking factor of the disease. Viruses enter the gland area through blood or lymphatic vessels. Inflammation occurs against the background of connective tissue proliferation, goiter formation. Often, fibrous changes spread not only to the gland, but also to nearby tissues and organs. A combination of Riedel thyroiditis with visceral fibromatoses is characteristic: sclerosing cholangitis, retrobulbar fibrosis, Ormond’s disease. This proves the systemic origin of the disease.
Most researchers consider a systemic infectious process that disrupts the production of collagen, protein molecules that are the basis of various types of connective tissues, as the pathophysiological basis of Riedel thyroiditis. Inflammation and reaction to infection trigger intensive cell division of fibrous tissue, which gradually replaces the thyroid parenchyma. A seal is formed – a goiter. Over time, connective tissue growths squeeze the esophagus, trachea, blood vessels, nearby muscles and nerves.
A decrease in hormonal activity is uncharacteristic, hypothyroidism can occur only with a prolonged course of the disease. The affected areas of the gland are similar to tumor-like formations, have a dense consistency, slightly bumpy surface. All or part of the glandular tissue is enclosed in a capsule. Gradually, connective tissue adhesions form between this capsule and adjacent organs.
Since the disease is chronic, the condition of patients remains satisfactory for a long time. The thyroid gland increases, thickens. There is no soreness. Changes occurring in the organ are subjectively not recognized for several years after the onset of the pathological process. The first symptoms occur when the goiter increases so much that it begins to squeeze the surrounding tissues or when fibrous tissue sprouts into nearby organs.
Patients complain of discomfort when swallowing, a feeling of compression, compression in the front of the neck, difficulty breathing, shortness of breath, hoarseness of voice, cough. Often they report the sensation of a coma or a foreign object in the throat. The severity of the clinical picture is due to the intensity of compression of the esophagus and trachea. So, in some patients, breathing unusually quickens with physical exertion, while others develop attacks of suffocation and progressive swallowing disorders at rest. For women, the limited mobility of the back of the tongue is more characteristic, for men – the immobility of the adam’s apple.
In the absence of treatment, connective tissue growths largely replace the parenchyma of the gland, as a result, hypothyroidism develops – insufficient hormone production. Protein and acid-base metabolism is disrupted, fluid is retained in the tissues, mucinous edema – myxedema is formed. There is a risk of degeneration of fibrous tissue into a malignant neoplasm, therefore, timely pathomorphological differential diagnosis is important, including a biopsy of the material from the affected area.
To make a diagnosis, the results of a comprehensive examination are used, including clinical, physical, instrumental and laboratory methods. The primary examination is performed by an endocrinologist. He finds out the symptoms of the disease (characterized by slow progression, respiratory disorders, swallowing, vocalization), clarifies the presence of other types of visceral fibromatoses. To confirm fibrotic goiter, exclude thyroid cancer, Hashimoto’s thyroiditis, the following methods are used:
- Examination, palpation. The size of the gland is enlarged, the surface is heterogeneous, bumpy, dense, hard, usually painless. Depending on the formation of adhesions and the stage of the disease, the gland is partially mobile or completely fixed. The skin of the affected area is unchanged. The skin easily gathers into a fold (it is not involved in the adhesive process). Submandibular lymph nodes of normal size.
- Echography. Ultrasound of the thyroid gland is shown to all patients. The method allows to estimate the volume of replacement of functional connective tissue. The increase in the size and densification of the gland, the thickening of the capsule revealed during physical examination is confirmed.
- Puncture biopsy. Due to the need to differentiate the fibrous and oncological process, most patients are recommended to have a biopsy with histological examination. The data confirm the good quality of the puncture material. In difficult cases, repeated (postoperative) examination of the tissues of the removed gland is carried out.
- Analysis for autoantibodies. As part of the differential diagnosis of fibrotic invasive and autoimmune thyroiditis, a laboratory test is prescribed to detect an increased titer of AT-TG and anti-TPO in the blood. In Riedel thyroiditis, the analysis data are negative.
Fibrous tissue is surgically removed. Due to the peculiarities of the course of the disease, the operation is carried out as planned. At the preparation stage, as well as in the postoperative period, patients are referred for dispensary observation to endocrinologists and surgeons. After surgery, patients are prescribed thyroid hormone and calcium preparations, vitamin D. The choice of treatment method depends on the stage of the disease and the prevalence of fibrosis:
- Extirpation of the isthmus of the gland. The isthmus is located closest to the larynx and is most susceptible to fibrosis, so its resection often helps to eliminate the symptoms of the disease. At the same time, the gland remains functionally active.
- Hemithyroidectomy. Removal of one lobe of the gland and the isthmus is recommended for unilateral fibromatous process. Hemithyroidectomy allows you to eliminate the disease while preserving the hormonal function of the gland. The remaining fraction after some time adapts to the needs of the body and begins to produce more hormones.
- Thyroidectomy. Complete removal of the gland is necessary with strong compression of the trachea, leading to suffocation, if it is impossible to exclude the malignancy of the neoplasm. Remove the gland tissue, all adhesions and splices. After the operation, a histological examination of the biomaterial will be performed. Patients are shown lifelong hormone replacement therapy.
Prognosis and prevention
Surgery is a fairly effective method of treating Riedel thyroiditis. The prognosis in most patients is favorable, the probability of relapse is low. To prevent the recurrence of fibromatosis, patients need periodic (at least once every six months) examinations by an endocrinologist. Prevention of the disease has not been developed, because there is no consensus on its causes. Persons from risk groups with fibrosis in other organs are recommended regular screening examinations for the purpose of early detection of thyroiditis.