What is Riedel Thyroiditis?
Riedel fibrosing thyroiditis is an uncommon condition where your thyroid gland suffers from long-term inflammation and scarring, also known as fibrosis. It is sometimes referred to as Riedel struma, ligneous struma, or chronic invasive fibrous thyroiditis. The typical symptoms of this condition include hypothyroidism, which is a state where your thyroid gland doesn’t produce enough hormones, and a thyroid gland that feels “hard-as-wood” and is not tender to touch.
As the condition progresses, the thyroid’s normal tissue and nearby structures are gradually replaced by tough, fibrous tissue. This destroys the follicular cells, the cells that produce hormones in the thyroid gland. Over time, the fibrous tissue can spread to nearby areas, like the airways, causing symptoms such as breathing difficulty (dyspnea), trouble swallowing (dysphagia), and a hoarse voice. This happens because the expanding fibrous tissue presses against the airways. The condition can also lead to hypothyroidism, hypoparathyroidism (where the parathyroid glands don’t make enough hormones), or Horner syndrome (a condition that affects the nerves to the eye and face).
Diagnosing Riedel fibrosing thyroiditis usually involves a physical exam, but it needs to be confirmed with a biopsy which is a test that examines a small sample of the thyroid tissue under a microscope. The biopsy would generally show an unusual amount of dense fibrous tissue mixed with a specific kind of white blood cells called eosinophils.
Treatment usually includes medication and potentially surgery for relieving symptoms. Steroid medications, like glucocorticoids, are the standard treatment and can often dramatically improve symptoms. But if these don’t work, other alternatives are medications like tamoxifen, mycophenolate, and sometimes, radiation. Surgery might be needed if other treatments don’t work, or if the condition has developed to a stage where it’s causing breathing difficulty due to compression of the airways.
What Causes Riedel Thyroiditis?
The cause of Riedel thyroiditis, a rare disease that involves a mass in the thyroid, is not fully understood. Some suggest it might be a variant of autoimmune thyroiditis, a condition where the body’s immune system attacks its own thyroid gland. Others believe it could be part of a systemic fibrosing disorder, which causes excess growth of connective tissue throughout the body, or linked with an immunoglobulin G4 (IgG4) related disease, where the body produces too much of a specific type of antibody.
The disease shows features like anti-thyroid antibodies (a protein made by the body to fight the thyroid), the presence of eosinophils (a type of white blood cell), and a good response to glucocorticoid therapy (a type of medication often used to treat inflammation), which make us think it could be an autoimmune disease. On the other hand, factors like the lack of other antibodies, no link with other autoimmune disorders, normal count of white blood cells, and normal levels of complement (proteins in the blood that help the immune system) suggest it might not be.
There are connections between Riedel thyroiditis and diseases like orbital fibrosis (scarring and inflammation around the eye), primary sclerosing cholangitis (inflammation and scarring of the bile ducts), and fibrosis of the tissue in the chest or abdomen, which makes us think it might be a part of a disease process that affects multiple areas of the body. Still, no clear association with other disorders involving excess growth of connective tissue consistently emerges, challenging this theory.
Risk Factors and Frequency for Riedel Thyroiditis
Riedel thyroiditis is a very rare disorder that causes inflammation of the thyroid, compared to other disorders like Hashimoto thyroiditis or subacute granulomatous thyroiditis. It’s estimated that Riedel thyroiditis affects about 1.06 people out of 100,000. This condition is most commonly found in adult women aged between 30 and 50 years old.
Signs and Symptoms of Riedel Thyroiditis
Riedel thyroiditis is a condition where the thyroid becomes hard and enlarged. It can cause a range of symptoms due to the involvement of various neck structures. These symptoms can include difficulty breathing if the trachea or windpipe is affected, problems swallowing due to the esophagus being involved, whistling sounds while breathing if the laryngeal nerve is affected, and potential venous sinus thrombosis (clots in the blood vessels) due to vasculature or blood vessels being involved. Eye bulging, also known as exophthalmos, can occur as a result of the disease affecting the tissues at the back of the eyeball.
During a doctor’s examination, they may feel a hard lump in the front part of the neck. It might not move when the patient swallows because it sticks to the structures in the neck. Showing positive Chvostek or Trousseau signs (which are specific physical symptoms) suggests hypoparathyroidism due to involvement of the parathyroid glands, a condition where the glands that control the body’s calcium levels are not working correctly.
Testing for Riedel Thyroiditis
In cases of Riedel thyroiditis, testing for thyroid function might show hypothyroidism, a condition where the thyroid gland is underactive, in roughly 74% of patients. Many patients with Riedel thyroiditis also have another condition called Hashimoto thyroiditis. In fact, about 90% of people with Riedel thyroiditis have positive thyroid peroxidase (TPO) antibodies, which is an indicator of Hashimoto thyroiditis. It’s very rare, but Riedel thyroiditis could also happen at the same time as Graves disease or subacute thyroiditis.
Doctors might also use an ultrasound of the neck to help diagnose Riedel thyroiditis. This test could reveal a low-echo, low-blood-flow mass involving the tissues outside of the thyroid gland, and sometimes encasing the carotid vessels, which are the main arteries in the neck. Elastography, another type of ultrasound, might show the presence of stiff, inflamed tissues which could suggest fibrosis, or scarring.
A computed tomography (CT) scan, a type of X-ray that provides detailed pictures of the body, could show the mass as having a lower density than the surrounding tissues and doesn’t become highlighted with contrast dye. CT scans can be more precise than ultrasounds in evaluating the involvement of tissues outside of the thyroid. A positron emission tomography (PET) scan may show increased uptake in areas of inflammation, which can be especially helpful in diagnosing far-ranging areas of fibrosis that may occur along with Riedel thyroiditis.
A definitive diagnosis can only be made by taking an open biopsy, where a small piece of tissue is removed and examined under a microscope. Fine needle aspiration (FNA), a procedure where a thin needle is inserted into a lump to withdraw cells, could reveal spindle-shaped cells and fragments of fibrotic tissue, but it’s often not enough on its own to make a diagnosis.
The diagnostic criteria for Riedel thyroiditis include:
1. The inflammation extends outside the thyroid gland.
2. There’s phlebitis, a condition where a vein becomes inflamed and potentially blocked with a blood clot.
3. Absence of granulomas (small inflammation spots), giant cells, lymphoid follicles (parts of the lymphatic system where immune cells gather), or oncocytes (abnormally large cells).
4. No signs of thyroid cancer.
Treatment Options for Riedel Thyroiditis
Riedel thyroiditis is a rare disease, and due to its infrequency, there isn’t a standardized treatment method based on outcome studies. One possible treatment approach is surgical removal of part or subtotal of the thyroid gland, but this is suggested only in cases where the disease is causing compression symptoms. Surgical treatment is complicated because of the difficulty in distinguishing between healthy thyroid tissue and the fibrotic (scar-like) issue caused by the disease. Even small surgical interventions can pose a significant risk, with complications reported in as many as 39% of cases. Therefore, surgery is usually recommended in as minimal form as possible to relieve compression symptoms.
The primary medication used to treat Riedel thyroiditis is glucocorticoids, a type of steroid that reduces inflammation. The effectiveness of glucocorticoids is usually prominent when used early in the disease progression. However, the patient’s response to this treatment can vary significantly. Some patients show dramatic improvement, seeing symptoms like voice changes and upper airway issues reversed. Others may not respond well to the medication, particularly when the illness has progressed significantly, and there’s an increase in fibrosis (scar tissue).
Another medication used in the treatment of Riedel thyroiditis and other disorders characterized by fibrosis is Tamoxifen. It works by activating a potent growth inhibitor called tumor growth factor-beta (TGF-ß). This medication, alone or in combination with glucocorticoids, has been found to reduce the size of the mass in the thyroid gland.
Mycophenolate mofetil is another medication used in some cases of Riedel thyroiditis. This immunosuppressive medicine has properties that combat fibrosis. It transforms into mycophenolic acid, which hinders the production of antibodies from T and B lymphocytes (types of white blood cells that play a significant role in immunity). In some resistant cases, it is combined with glucocorticoids for effective outcomes. However, to firmly establish its effectiveness and role in treating Riedel thyroiditis, more studies on this medication are required.
What else can Riedel Thyroiditis be?
If a person has a mass in the front of their neck, it’s important to figure out whether it’s Riedel thyroiditis or another type of condition that could also spread to the tissues around the thyroid. These could include illnesses like anaplastic thyroid carcinoma, thyroid lymphoma, and thyroid sarcoma.
Anaplastic carcinoma is a fast-growing cancer that typically occurs in older people and can make it seem like someone has Riedel thyroiditis because it can cause the same difficulty swallowing or feelings of choking. One big difference is that people with anaplastic carcinoma are typically older, anywhere from 70 to 80 years of age, while younger women around 50 years old are more prone to Riedel thyroiditis. Also, when doctors take a small sample of cell (a biopsy) or perform a fine needle aspiration (FNA), they don’t find cancer cells in those with Riedel thyroiditis.
Other conditions to consider are a type of Hashimoto thyroiditis that causes inflammation and scarring. Some of the signs that it might be this condition instead of Riedel thyroiditis include:
- High levels of antibodies that attack the thyroid
- The presence of a particular type of cell called Hurthle cells
- No spread of the disease outside of the thyroid
- Inflammation of the veins (phlebitis)
What to expect with Riedel Thyroiditis
This condition typically has a favourable outcome. In some cases, the disease can remain stable for years, but it can also become aggressive and progress quickly after a trigger.
There’s usually a delay in diagnosis up to 2 years because the disease is quite rare and develops gradually, often without showing clear signs. The main cause of death associated with this condition typically results from pressure on the windpipe (trachea).
Older studies reported that the rate of death specific to this disease ranges from 6 to 10%. Nevertheless, a recent study from Mayo Clinic found no increase in mortality over a follow-up period of 9.5 years, with about 86% of patients remaining stable.
Possible Complications When Diagnosed with Riedel Thyroiditis
: Riedel thyroiditis complications are generally caused by the damage to tissues surrounding the thyroid, driven by fibrosis, a type of tissue scarring. Symptoms include breathing difficulties, wheezing, and potentially respiratory failure due to throat constriction. The closure of neck veins might lead to blood clots. Damage to the nerve cluster known as the sympathetic trunk can cause Horner syndrome, an eye disorder. About 14% of patients experience issues with the parathyroid glands, causing a condition known as hypoparathyroidism, where the body lacks enough parathyroid hormone.
Additionally, Riedel thyroiditis can coincide with other disorders characterized by fibrosis. Chest issues, including thoracic fibrosis, may present as superior vena cava (SVC) syndrome due to SVC blockage. Next, fibrosis in the region behind the peritoneum, or retroperitoneum, can cause back or side pain due to hydroureteronephrosis, a condition causing dilation of the kidneys. Fibrosis may also result in stomach distress due to disorders like sclerosing cholangitis or pancreatic fibrosis. In some cases, issues such as exophthalmos, or bulging eyes, can be an early indicator of Riedel thyroiditis due to involvement of tissues behind the eye.
Health issues resulting from Riedel Thyroiditis:
- Breathing difficulties
- Wheezing or respiratory failure
- Blood clots
- Horner syndrome
- Hypoparathyroidism
- Chest issues (SVC Syndrome)
- Back or side pain (hydroureteronephrosis)
- Stomach distress from sclerosing cholangitis or pancreatic fibrosis
- Bulging eyes (Exophthalmos)
