An Overview of Acute Infectious Thyroiditis

Woman rubbing sore neck
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Acute infectious thyroiditis is a rare thyroid gland infection. This type of infection is painful, associated with a fever, and progresses rapidly. It can affect children and adults, but it is more common among children. If you or your child develops acute infectious thyroiditis, it can worsen and produce an abscess if left untreated. This infection is treated with antibiotics or a procedure that drains the fluid and pus.

Symptoms

Acute infections, by definition, are the type of infections that cause unpleasant symptoms within a short period of time. If you or your child develop acute infectious thyroiditis, you can expect the effects to rapidly worsen.

Symptoms may include:

  • Rapid onset of pain and tenderness in one side of your neck
  • Fever and chills (a flu-like feeling)
  • Enlarged thyroid gland or an enlargement in your neck area
  • A movable lump in your neck
  • A warm, red, or tender area in the neck
  • Painful swallowing
  • Swollen lymph glands

You can also develop symptoms of hypothyroidism (low thyroid hormone function) or hyperthyroidism (excess thyroid hormone function), although your thyroid function is likely to remain stable during a bout of acute infectious thyroiditis. 

Complications

Acute infectious thyroiditis can produce a number of complications, the most common of which is an abscess, an encapsulated (closed off) infection that is difficult to treat with antibiotics.

Systemic infection, which is the spread of the infection to another part of your body, is a rare complication. Bleeding into the thyroid gland can occur, resulting in swelling, possible respiratory symptoms, and damage to the thyroid gland. While it is uncommon, long-term thyroid dysfunction due to damage to the thyroid gland can occur after the infection is completely resolved

Causes

Infectious thyroiditis is usually caused by a bacterial infection. The most commonly identified bacteria is Staphylococcus aureus, and Streptococcus bacterial species and other Staphylococcus bacteria can cause the infection as well. Less commonly, acute infectious thyroiditis can be caused by mycobacteria or fungi.

Acute infectious thyroiditis is rare because the thyroid gland is inherently better protected from infection than most other regions of the body. There are some risk factors that can increase your chances of developing an acute thyroid infection, however.

Risk factors include:

  • Time of year: This infection is more common in the fall and winter, especially after another infection of the upper respiratory tract.
  • Age: It is more common in children. Those who have a piriform sinus fistula, which is a congenital (from birth) defect in the areas around the nose, mouth, and neck, are at increased risk of developing this infection. The fistula can permit bacterial organisms to have access to the thyroid gland. Only about 8 percent of acute infectious thyroiditis is estimated to occur in adults.
  • Weakened immune system: You are at a higher risk if you take immunosuppressive medication, chemotherapy drugs, or have a medical condition such as HIV.
  • Thyroid cancer increases the risk of developing an acute thyroid infection.
  • Intravenous (IV) drug use makes you more susceptible to developing a severe bacterial infection and has been associated with acute infectious thyroiditis.

While thyroid gland infection is rare, subacute or chronic thyroid infections are more common and less severe than acute infectious thyroiditis. Acute infectious thyroiditis is usually caused by bacteria, whereas subacute and chronic thyroid infections are usually caused by a virus, and are therefore treated with different medications.

Diagnosis

If your doctor suspects that you have acute infectious thyroiditis, you will need a medical evaluation to confirm the diagnosis and to identify whether you have any risk factors. Because a fever and pain in your neck region are likely to be the most noticeable symptoms, your doctor will evaluate your neck and look for signs of infection elsewhere in the body.

Physical Examination

Along with a thorough general physical examination, your doctor will gently palpate (feel) your neck and thyroid gland, as well as nearby lymph nodes to check the size and texture of any growth.

Diagnostic Imaging Tests

Even if you don't have a detectable abnormal thyroid gland on your physical examination, your doctor is likely to order one or more imaging tests to visualize the structures in your neck. Diagnostic examinations may include a neck ultrasound, computerized tomography (CT) scan, or magnetic resonance imaging (MRI).

These imaging tests can help identify whether your symptoms are caused by thyroiditis or by another infection or disease involving the neck. Anatomical variations, like a fistula, can be identified as well.

Sometimes, imaging tests can help identify whether thyroiditis is suppurative (contains pus) or non-suppurative. The difference is that suppurative infectious thyroiditis is usually acute and more severe than non-suppurative thyroiditis, which is usually chronic.

Blood Tests

You may need blood tests, specifically a complete cell count (CBC), which can show an elevated white blood cell count with an infection, and thyroid function tests, which are usually altered by non-infectious inflammation of the thyroid gland, like non-infectious thyroiditis.

In addition to identifying the bacterial cause of your infection (or another microorganism), your doctor may also run blood tests to identify whether you have an undiagnosed problem with your immune system.

Fine Needle Aspiration

Fine needle aspiration (FNA) is a procedure that involves withdrawing some of the fluid or tissue from your thyroid gland. In some cases, the FNA is guided by ultrasound to determine the position and location of an infection or abscess.

The sample will be analyzed using a culture, which is a material that allows infectious organisms to grow so that they can be identified. The culture results can help your doctor choose the appropriate antibiotic and/or anti-fungal medication for treatment.

Treatment

The treatment of acute thyroiditis is focused on eliminating the infection and reducing symptoms while the infection resolves. There are several treatments that can be used, and, if you or your child has acute infectious thyroiditis, your doctors will initiate treatment quickly.

Oral antibiotics can be used for acute infectious thyroiditis. Some of the antibiotic medications that are commonly used for this type of infection include penicillin, ampicillin, or methicillin.

If your doctor is concerned that you could have an antibiotic-resistant infection, another antibiotic may be selected. Antibiotic-resistant infections are bacteria that do not respond to standard antibiotics, often called "superbugs," and they require treatment with antibiotics that are stronger and/or more specifically directed.

You may need treatment with an intravenous (IV) antibiotic if your doctor is concerned that your infection is progressing rapidly, if you can't swallow oral medication, or if you are vomiting so much that you can't absorb oral medication.

Percutaneous drainage is a procedure that your doctor may use to remove the infectious fluid with a needle. You may have percutaneous drainage at the same time as your FNA. If you have this procedure, you will probably also receive antibiotic treatment.

Infrequently, surgical drainage of an infection or an abscess is required if your infection does not improve with percutaneous drainage and antibiotic therapy.

Rarely, surgical removal of part of the thyroid gland may be needed as well. In some cases, removal of half the thyroid gland, known as a lobectomy, may provide more effective treatment.

In addition to treatment for your infection, you may also need medication to lower your fever and/or treatment for pain. If you are unable to eat, you may need IV fluids until you are able to resume eating.

A Word From Verywell

Infection of the thyroid gland is rare. If you are diagnosed with this type of infection, you can anticipate a rapid treatment and a quick recovery. Thyroid infections generally respond well to treatment, although there is a risk of recurrence if there is an associated fistula.

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