Acute Suppurative / Infectious Thyroiditis

hyperthyroidism-part1-by-dr-bashir-associate-professor-medicine-sopore-kashmir-35-638

  • Introduction:
    • Infectious thyroiditis is also known as:
      • Acute thyroiditis
      • Suppurative thyroiditis
      • Bacterial thyroiditis
      • Pyogenic thyroiditis
    • Bacterial infections of the thyroid are extremely rare:
      • With only:
        • 224 cases having been reported in the literature from 1900 to 1980 (adult literature)
        • 60 cases reported in the pediatric literature
      • Bacterial infections:
        • Are the most common causes of infectious thyroiditis
        • The infections are generally:
          • Suppurative and acute
    • Infectious thyroiditis caused by:
      • Fungal and parasitic infections:
        • Are more frequently chronic and indolent
  • Etiology and Pathogenesis:
    • The thyroid gland’s high iodine content, significant vascularity, lymphatic drainage as well as its protective capsule:
      • Provide the thyroid gland with notable resistance to infection
    • The most common predisposing factor to infections of the thyroid appears to be:
      • Preexisting thyroid disease has been observed in up to two thirds of women and one half of men with infectious thyroiditis:
        • Simple goiter
        • Nodular goiter
        • Hashimoto’s thyroiditis
        • Thyroid carcinoma
      • Patients with the acquired immunodeficiency syndrome (AIDS):
        • Are a population particularly at risk for bacterial thyroiditis:
          • As with other opportunistic infections in AIDS patients, infections of the thyroid gland often are chronic and insidious in onset
    • In the adult:
      • Staphylococcus aureus and Streptococcus pyogenes are the offending pathogens:
        • In more than approximately 80% of patients:
          • And are the sole pathogen in over 70% of cases
    • In children:
      • Alpha- and beta-hemolytic Streptococcus and a variety of anaerobes:
        • Account for approximately 70% of cases:
          • Whereas mixed pathogens are identified in greater than 50% of cases
    • Other thyroidal bacterial pathogens that have been shown to cause infectious thyroiditis include:
      • Salmonella brandenburg
      • Salmonella enteritidis
      • Actinomyces naeslundi
      • Actinobacillus actinomycetemcomitans
      • Brucella melitensis
      • Clostridium septicum
      • Eikenella corrodens
      • Enterobacter
      • Escherichia coli
      • Haemophilus influenzae
      • Klebsiella sp.
      • Pseudomonas aeruginosa
      • Serratia marcescens
      • Acinetobacter baumannii
      • Staphylococcus nonaureus
    • Pathogenesis of Acute Suppurative Thyroiditis:
      • Bacterial:
        • 68% of the cases
      • Parasitic:
        • 15% of the cases
      • Mycobacterial:
        • 9% of the cases
      • Fungal:
        • 5% of the cases
      • Syphilitic:
        • 3% of the cases
    • Infection and suppuration may result from:
      • Direct spread from a nearby infection
      • Via the bloodstream
      • Via the lymphatics
    • The seminal observation regarding the pathogenesis of bacterial thyroiditis was made in 1979 when Takai et al.:
      • Who reported seven cases of infectious thyroiditis:
        • Caused by a fistula originating from the left pyriform sinus
      • Subsequently, studies involving more than 100 patients with infectious thyroiditis:
        • Have identified pyriform sinus fistulae:
          • Primarily left-sided, in up to 90% of these patients, especially in those with recurrent episodes
    • Additional reports identified as routes of thyroidal infection:
      • Infected embryonic cysts from the third and fourth brachial pouches
      • Thyroglossal duct cysts  
    • On pathologic exam:
      • The characteristic changes of acute bacterial inflammation, including :
        • Necrosis and abscess formation:
          • Are commonly found
  • Clinical Manifestations:
    • Bacterial thyroiditis is often preceded by an upper respiratory infection:
      • Which may induce inflammation of the fistula and promote the transmission of pathogens to the thyroid.
    • Consistent with these observations:
      • Bacterial thyroiditis is more common:
        • In the late fall and late spring months
    • Over 90% of patients will present with:
      • Thyroidal pain:
        • The pain is often referred diffusely to adjacent structures
      • Tenderness
      • Fever
      • Local compression resulting in dysphagia and dysphonia
      • Systemic symptoms are frequently seen, such as:
        • Fever
        • Chills
        • Tachycardia
        • Malaise
  • Laboratory Findings:
    • Thyroid function tests are usually normal:
      • However:
        • Cases of hypothyroidism and thyrotoxicosis have been reported
    • The polymorphonuclear leukocyte count and the sedimentation rate:
      • Are usually elevated
    • The organism frequently can be identified by:
      • Gram stain and culture of a fine-needle aspiration in the region of suppuration:
        • Although sterile cultures are seen in approximately 8% of cases
  • Imaging:
    • A nuclear medicine thyroid scan:
      • May show the suppurative region as a “cold” area
    • Ultrasound examination may reveal:
      • A cystic or “complex” nodule

thyroiditis-by-dr-selim-14-638

  • Diagnosis:
    • The diagnosis is made with:
      • A fine-needle aspiration
      • Gram stain
      • Culture
    • Symptomatically:
      • Infective thyroiditis may be difficult to differentiate from subacute thyroiditis in the early phases:
        • Although the characteristic thyroid function changes in the latter disease should be helpful in discriminating the two
    • Leukocytosis and an elevated erythrocyte sedimentation rate are not discriminatory tests:
      • As they are commonly observed in both subacute thyroiditis and infectious thyroiditis
    • In general:
      • Patients with bacterial thyroiditis have a greater febrile response than those with subacute thyroiditis
    • Once abscess formation has occurred:
      • The local redness, lymphadenopathy, hyperpyrexia, and leukocytosis should lead to the correct diagnosis
    • Malignant neoplasms and hemorrhages into cysts:
      • May sometimes present with manifestations that mimic this disorder
  • Clinical Management:
    • The prognosis of bacterial thyroiditis:
      • Is often dependent on the prompt recognition and treatment of this disorder:
        • As mortality may approach 100%:
          • If the diagnosis is delayed and appropriate antimicrobial therapy is not instituted
      • Much depends on the identification of the microorganism:
        • From the needle aspirate, incision, and drainage, or occasionally from blood culture
        • If no organisms are seen on the Gram stain:
          • Nafcillin and gentamicin or a third-generation cephalosporin is the appropriate initial therapy in adults
          • A second-generation cephalosporin or clindamycin is reasonable in children
        • If an abscess develops and prompt response to antibiotics does not occur:
          • Incision and drainage are necessary:
            • Sometimes partial lobectomy must be performed,:
              • Especially if the disease is recurrent
        • Usually the lesions heal with reasonable speed after initiation of the correct antimicrobial agent, and recurrences are uncommon.
        • Mortality from acute bacterial thyroiditis has markedly improved from the 20% to 25% reported in the early 1900s:
          • With the extensive review by Berger estimating an overall mortality of 8.6%
          • In one review of more than 100 patients, mortality as a complication of acute bacterial thyroiditis was not listed

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