Acute infectious thyroiditis (AIT) also known as suppurative thyroiditis, microbial inflammatory thyroiditis, pyrogenic thyroiditis and bacterial thyroiditis.Melmed, Shlomo, Kenneth S. Polonsky, and P. R. Larsen
thyroiditis vs subacute thyroiditis diagnosis criteria
"Acute InfectiousThyroiditis." Willams Textbook of Endocrinology. By Henry M. Kronenberg. 11th ed. Philadelphia: Elsevier, 2008. 945-47.Lazarus, John, and James Hennessey. "Acute and Subacute, and Reidel’s Thyroiditis." Ed. Leslie J. De Groot. The Thyroid And Its Diseases. 6th ed. New York: Elsevier, 1996. The

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The ...

is normally very resistant to infection. Due to a relatively high amount of

iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , ...

in the tissue, as well as high vascularity and lymphatic drainage to the region, it is difficult for pathogens to infect the thyroid tissue. Despite all this, a persistent fistula from the

piriform sinus On either side of the laryngeal orifice in humans is a recess, termed the pyriform sinus (also piriform recess, piriform sinus, piriform fossa, or smuggler's fossa), which is bounded medially by the aryepiglottic fold, laterally by the thyroid car ...

may make the left lobe of the thyroid susceptible to infection and abscess formation. AIT is most often caused by a bacterial infection but can also be caused by a fungal or parasitic infection, most commonly in an immunocompromised host.

Signs and symptoms

In most cases AIT is characterized by onset of pain, firmness, tenderness, redness or swelling in the anterior aspect of the neck. Patients will also present with a sudden fever,

difficulty swallowing Dysphagia is difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right. It may be a sensation that suggests difficulty in the passage of solids or liqui ...

and difficulty controlling the voice. Symptoms may be present from 1 to 180 days, with most symptoms lasting an average of about 18 days. The main issue associated with the diagnosis of AIT is differentiating it from other more commonly seen forms of thyroid conditions. Pain, fever and swelling are often much more severe and continue to get worse in people who have AIT compared to those with other thyroid conditions.

Causes

Despite the thyroid gland being extremely resistant to infection, it is still susceptible to infection by various bacteria.Park, Sun W., Moon H. Han, Myung H. Sung, In O. Kim, Kwang H. Kim, Kee H. Chang, and Man C. Han. "Neck Infection Associated with Pyriform Sinus Fistula: Imaging Findings." American Journal of Neuroradiology Am J Neuroradiol 21 (2000): 817-22. The cause can be almost any bacterium. ''

Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often posit ...

'', ''

Streptococcus pyogenes ''Streptococcus pyogenes'' is a species of Gram-positive, aerotolerant bacteria in the genus '' Streptococcus''. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They ...

'', ''

Staphylococcus epidermidis ''Staphylococcus epidermidis'' is a Gram-positive bacterium, and one of over 40 species belonging to the genus '' Staphylococcus''. It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbi ...

'', and ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They ar ...

'' in descending order are the organisms most commonly isolated from acute thyroiditis cases in children. Other aerobic organisms are ''Klebsiella sp'', '' Haemophilus influenza'', ''

Streptococcus viridans The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates (hence the name "viridans", from Latin "vĭrĭdis", green), although s ...

'', ''

Eikenella corrodens ''Eikenella corrodens'' is a Gram-negative facultative anaerobic bacillus that can cause severe invasive disease in humans. It was first identified by M. Eiken in 1958, who called it ''Bacteroides corrodens''. ''E. corrodens'' is a rare pericar ...

'', ''

Enterobacteriaceae Enterobacteriaceae is a large family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but o ...

'',Brook, I. (2002). "Microbiology and management of acute suppurative thyroiditis in children." ''International Journal of Pediatric Otorhinolaryngology'', 67, 447-451. and ''salmonella sp''.3) Lazarus, John, and James Hennessey. "Acute and Subacute, and Reidel’s Thyroiditis." Ed. Leslie J. De Groot. The Thyroid And Its Diseases. 6th ed. New York: Elsevier, 1996 Occurrences of AIT are most common in patients with prior thyroid disease such as

Hashimoto's thyroiditis Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis and Hashimoto's disease, is an autoimmune disease in which the thyroid gland is gradually destroyed. Early on, symptoms may not be noticed. Over time, the thyroid may enlarg ...

thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck. Ca ...

. The most common cause of infection in children is a congenital abnormality such as pyriform sinus

fistula A fistula (plural: fistulas or fistulae ; from Latin ''fistula'', "tube, pipe") in anatomy is an abnormal connection between two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other hollow or ...

. In most cases, the infection originates in the piriform sinus and spreads to the thyroid via the fistula.Yamada, H., Fujita, K., Tokuriki, T., & Ishida, R. (2002). "Nine cases of piriform sinus fistula with acute suppurative thyroiditis." Elsevier, 29, 361-365. In many reported cases of AIT the infection occurs following an

upper respiratory tract infection An upper respiratory tract infection (URTI) is an illness caused by an acute infection, which involves the upper respiratory tract, including the nose, sinuses, pharynx, larynx or trachea. This commonly includes nasal obstruction, sore thro ...

. One study found that of the reported cases of AIT, 66% occurred after an acute illness involving the upper respiratory tract. Although the rates of infection are still very low, cases of AIT have been on the rise in recent years due to the higher occurrence of immune-compromised patients. Other causes of AIT are commonly due to contamination from an outside source and are included below. * Repeated fine needle aspirates * Perforation of

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to t ...

* Regional infection

Diagnosis

Patients who are suspected of having AIT often undergo tests to detect for elevated levels of

white blood cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

as well as an

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

to reveal unilobular swelling. Depending on the age and immune status of the patient more invasive procedures may be performed such as fine needle aspiration of the neck mass to facilitate a diagnosis. In cases where the infection is thought to be associated with a sinus fistula it is often necessary to confirm the presence of the fistula through surgery or laryngoscopic examination. While invasive procedures can often tell definitively whether or not a fistula is present, new studies are working on the use of computed tomography as a useful method to visualize and detect the presence of a sinus fistula.

Diagnostic tests

* Fever, redness, swelling * Pain * Blood tests of thyroid functions including TSH, T4 and T3 are usually normal * Ultrasonographic examination often shows the abscess or swelling in thyroid *

Gallium scan A gallium scan is a type of nuclear medicine test that uses either a gallium-67 (67Ga) or gallium-68 (68Ga) radiopharmaceutical to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and galli ...

will be positive *

Barium swallow An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as bar ...

will show fistula connection to the piriform sinus and left lobe * Elevated white blood cell count * Elevated erythrocyte sedimentation rate * Fine-needle aspiration

Subtypes of thyroiditis

Treatment

Treatment of AIT involves antibiotic treatment. Based on the offending organism found on microscopic examination of the stained fine needle aspirate, the appropriate antibiotic treatment is determined. In the case of a severe infection, systemic antibiotics are necessary.

Empirical Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...

broad spectrum

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

treatment provides preliminary coverage for a variety of bacteria, including ''S. aureus'' and ''S. pyogenes.'' Antimicrobial options include penicillinase-resistant penicillins (ex:

cloxacillin Cloxacillin is an antibiotic useful for the treatment of a number of bacterial infections. This includes impetigo, cellulitis, pneumonia, septic arthritis, and otitis externa. It is not effective for methicillin-resistant ''Staphylococcus aureus ...

dicloxacillin Dicloxacillin is a narrow-spectrum β-lactam antibiotic of the penicillin class. It is used to treat infections caused by susceptible (non-resistant) Gram-positive bacteria.Product Information: DICLOXACILLIN SODIUM-dicloxacillin sodium capsule. T ...

) or a combination of a penicillin and a beta-lactamase inhibitor. However, in patients with a penicillin allergy,

clindamycin Clindamycin is an antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear in ...

or a

macrolide The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Ma ...

can be prescribed. The majority of anaerobic organisms involved with AIT are susceptible to penicillin. Certain

Gram-negative bacilli Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

(ex: ''

Prevotella ''Prevotella'' is a genus of Gram-negative bacteria. ''Prevotella'' spp. are members of the oral, vaginal, and gut microbiota and are often recovered from anaerobic infections of the respiratory tract. These infections include aspiration pn ...

'', ''

Fusobacteriota Fusobacteriota are obligately anaerobic non-sporeforming Gram-negative bacilli. Since the first reports in the late nineteenth century, various names have been applied to these organisms, sometimes with the same name being applied to different ...

'', and '' Porphyromonas'') are exhibiting an increased resistance based on the production of beta-lactamase. Patients who have undergone recent penicillin therapy have demonstrated an increase in beta-lactamase-producing (anaerobic and aerobic) bacteria. Clindamycin, or a combination of

metronidazole Metronidazole, sold under the brand name Flagyl among others, is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vaginosis. It is ...

and a macrolide, or a penicillin combined with a beta-lactamase inhibitor is recommended in these cases. Fungal thyroiditis can be treated with

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis ...

and

fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prev ...

. Early treatment of AIT prevents further complications. However, if antibiotic treatment does not manage the infection, surgical drainage is required. Symptoms or indications requiring drainage include continued fever, high white blood cell count, and continuing signs of localized inflammation. The draining procedure is also based on clinical examination or ultrasound/ CT scan results that indicate an

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends ...

or gas formation. Another treatment of AIT involves surgically removing the fistula. This treatment is often the option recommended for children. However, in cases of an antibiotic resistant infection or necrotic tissue, a

lobectomy Lobectomy means ''surgical excision of a lobe''. This may refer to a lobe of the lung (also simply called a lobectomy), a lobe of the thyroid ( hemithyroidectomy), a lobe of the brain (as in anterior temporal lobectomy), or a lobe of the liver ...

is recommended. If diagnosis and/or treatment is delayed, the disease could prove fatal.

Epidemiology

Acute infectious thyroiditis is very rare, with it only accounting for about 0.1–0.7% of all

thyroiditis Thyroiditis is the inflammation of the thyroid gland. The thyroid gland is located on the front of the neck below the laryngeal prominence, and makes hormones that control metabolism. Signs and symptoms There are many different signs and sympto ...

. Large hospitals tend to only see two cases of AIT annually. For the few cases of AIT that are seen the statistics seem to show a pattern. AIT is found in children and young adults between the ages of 20 and 40. The occurrence of the disease in people between 20 and 40 is only about 8% with the other 92% being in children. Men and women are each just as likely to get the disease. If left untreated, there is a 12% mortality rate.

References

External links

{{Thyroid disease Thyroid disease