Acute suppurative thyroiditis with thyrotoxicosis caused by methicillin resistant Staphylococcus aureus.
Acute suppurative thyroiditis (AST) and thyroid abscess are relatively rare. This may be partially due to an inherent resistance of the thyroid gland to infection because of its rich blood supply, high iodine content, encapsulation and extensive lymphatic drainage. (1-3) Bacterial infection with Staphylococcus and Streptococcus species are the most common causes of AST. Occasionally, the thyroid gland can be infected with fungi, parasites, or mycobacterium. (1-3) Less common causes of suppurative thyroiditis include Acinetobacter, Salmonella, Klebsiella, Pseudomonas, Brucella species, Pasturella species, as well as E. coli. (3) Here we describe a case of thyrotoxicosis associated with rapidly progressive thyroid abscess caused by hematogenously disseminated Staphylococcus aureus in a patient with end stage renal disease (ESRD).
A 43-year-old African American woman with end stage renal disease presented to the emergency department with a 4 day history of fever, chills and sore throat. Recent medical history included uneventful placement of a hemodialysis catheter 3 weeks ago. The sore throat did not respond to supportive care and rapidly progressed to include dysphagia, odynophagia and left sided neck pain. Patient had no history of head and neck irradiation or neck trauma. She was found to have a minimally enlarged thyroid gland on an unrelated CT scan several months prior to presentation. She had a 20 pack-year history of cigarette smoking and intravenous cocaine abuse. On examination, her oral temperature was 39[degrees]C, supine blood pressure was 160/100 mmHg, and pulse rate was 110 beats per minute. She had a symmetrically enlarged thyroid gland with significant tenderness over the left lobe. No overlying skin erythema, warmth or fluctuation were appreciated at this time. The rest of the physical exam was significant for fine tremor of both upper extremities and brisk deep tendon reflexes. Thyroid function tests confirmed thyrotoxicocis and the rest of her laboratory studies during current and previous admissions are shown in Table 1. Patient was started on intravenous (IV) vancomycin and ampicillinsulbactam, due to suspicion of thyroid abscess.
Thyroid ultrasound was performed the next morning. It showed diffusely enlarged gland with mixed hyper- and hypoechoic areas without definite nodules or an increase in blood flow. CT scan of the neck showed extensive inflammatory changes involving the thyroid gland and surrounding tissues, as well as evolving thyroid abscess, extending to the left retropharyngeal area (Figure 1). Blood cultures from both peripheral and hemodialysis catheters were positive for methicillin resistant Staphylococcus aureus (MRSA). Fine needle aspirates (FNA) from the thyroid gland showed numerous polymorphonuclear cells on Gram stain (Figure 2), while the culture was positive for MRSA. The hemodialysis catheter was removed and culture of the catheter tip also grew MRSA. At this time, antibiotic treatment was changed to IV vancomycin and clindamycin. Metoprolol was added to control tachycardia. Acute bacterial endocarditis was ruled out by trans-thoracic echo (TTE).
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On the third day of admission, she developed acute respiratory distress and was intubated. Repeat contrast neck CT and MRI (Figure 3) studies showed septated neck abscess progressively spreading towards upper mediastinum through the retropharyngeal space with significant displacement of the trachea. At this point, the patient underwent emergent neck exploration and abscess drainage. The culture from the drainage was positive for MRSA with resistance profile identical to all previous cultures. Patient's condition as well as thyroid tests significantly improved after the drainage (Table 1). Two days after abscess drainage, she was successfully extubated and later discharged to nursing home in order to complete the course of intravenous antibiotics treatment.
A pyriform sinus fistula is the most common source of infection, causing AST in children and adolescents. (2) It is often preceded by cough, upper respiratory infection and otitis media. (4) In adults, AST results from the hematogenous or lymphatic spread of microbial agents. (1,5) Other less common causes of AST with or without abscess formation include direct trauma from fine needle aspiration or foreign bodies, such as chicken or fish bones (1) and septic emboli from infective endocarditis. (6)
There is an annual 6-8% increase in the incidence of ESRD in the United States, accounting for about 300,000 patients currently treated by hemodialysis. (7) While tunneled hemodialysis catheters have become increasingly common as a permanent source of vascular access, used in almost a quarter of all hemodialysis patients, they are known to associate with increased morbidity and mortality when compared to arteriovenous fistulas. (8-11) It is estimated that almost 30% of patients using a catheter had an episode of catheter-related infection (bacteremia or sepsis) annually. (8,12) Bacteria infect the catheter either by luminal or extra-luminal sites. Extra-luminal infection or colonization is mostly from the skin flora at the site of insertion, whereas luminal contamination is from improper handling of the access by patients, hemodialysis or other medical staff. (8,12)
Gram positive organisms are responsible for the majority of catheter-related infections and S. aureus and coagulase negative staphylococcus account for 40-80% of these infections. (11,12) S. aureus is a leading cause of infections in ESRD patients, causing an estimated 27-39% of all bacteremias in this population, while an estimated 15-66% of all S. aureus bacteremia occur in patients with ESRD. (13) Several factors increase the risk of catheter-related infections and include nasal colonization of S. aureus, catheter colonization, prolonged use of the catheter, history of catheter-related infection, diabetes mellitus and iron overload. (11,12) Catheter-related infection is associated with the formation of biofilms, which are formed as early as 24 hours after placement of a catheter and is associated with increased resistance to antibiotics, host defenses and are suspected to promote bacterial growth. One of the important characteristic of S. aureus in relation to pathogenesis of catheter-related bacteremia is its ability to persist in biofilms. (9,13)
S. aureus is known to colonize approximately half of the patients on dialysis. S. aureus carrier state in hemodialysis patients is associated with a fourfold increase of vascular access infections and mortality from sepsis is almost 100-300 times higher in hemodialysis patients than in the general population. (13) A majority of the morbidity and mortality associated with catheter-related infections is from metastatic infection, which can occur in up to 50% of patients. The risk of complications is higher if the infection is due to S. aureus and includes endocarditis, osteomyelitis and abscess formation. (11) A recent study concluded that the incidence of methicillin resistant staphylococcus aureus (MRSA) infection in hemodialysis patients to be as high as 45 per 1000 population, when compared to the general population which had an incidence of less than 0.5 per 1000 population. (11) The length of hospitalization for ESRD patient with S. aureus bacteremia was about 12 days with incurred costs of around $20,000 with overall mortality of 20%. (14) Although it is sometimes impossible to determine the exact cause of bacteremia, we can speculate that in our patient, placement of hemodialysis catheter was associated with thyroid seeding of MRSA with subsequent abscess formation and spill-over bacteremia as evidenced from cultures of all examined sources. Possibility of viral thyroiditis with secondary superinfection with MRSA from pre-existent low-grade bacteremia could not be excluded.
Thyroid abscess has been reported more often in women than in men, and is more common before the age of 40. (15) Approximately half of patients with AST have preexisting thyroid disease. AST typically presents with acute neck pain, fever, dysphagia and dysphonia. It can be difficult to distinguish AST from subacute thyroiditis (SAT): both are associated with a tender thyroid gland, fever, leukocytosis, and increased ESR. Patients with AST usually have normal TFT in absence of thyroid disease, however in rare cases, severe destructive AST can be associated with thyrotoxicosis. (15-18) Interestingly, our patient did not have any history of thyroid disease in the past, but she was thyrotoxic due to destruction of thyroid follicles resulting in release of thyroid hormones into the circulation. This phenomenon is usually transient and expected to resolve completely upon recovery. (4) A recurrent left neck abscess or bacterial thyroiditis should raise the suspicion for persistent pyriform fistula. (19) Barium swallow has sensitivity of about 80% to demonstrate the presence of anomalous tract (4), false negative results may occur when infection is associated with extensive edema. (20)
This case demonstrated that a high index of clinical suspicion is necessary for timely diagnosis of this potentially devastating disease. AST should be considered in the differential diagnosis of an acute inflammatory process of the thyroid, although this condition is rare, especially with current widespread antibiotic use. Delay in diagnosis and treatment of AST leads to recurrence or rupture of abscess to other fascial spaces, sepsis, and internal jugular vein thrombosis. (21) Computed tomography or MRI of the neck could assess the extent of infection and guide the decision towards surgical intervention, especially if a rapid progression or potential compromise of mediastinal structures is seen on serial studies. (22) While parental antibiotics treatment is the mainstay of treatment of AST, as our case illustrates, urgent surgical intervention is mandatory, when a rapid progression of the disease with signs of compression or mediastinal spread occurs.
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Vitaly Kantorovich, Naveen Patil, Negah Rassouli
Division of Endocrinology and Metabolism, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
Corresponding author: Vitaly Kantorovich, M.D.
Division of Endocrinology and Metabolism
Department of Internal Medicine
University of Arkansas for Medical Sciences
4301 West Markham St., Slot #587
Little Rock, AR 72205-719
Phone: (501) 686-5130
Fax: (501) 686-8148
Table 1. Thyroid Function Tests 3 months On 1 week 3 weeks prior to admission later later admission TSH (0.3-5.5 ulU/mL) 3.9 2 0.07 0.03 FT4 (0.5-1.6 ng/dL) 4.70 4.87 1.90 FT3 (2.3-4.9 pg/mL) 24.7 10.7 Anti TPO Ab (0-60 UI/mL) 28 Thyroblobulin Ab (0-25 UI/mL) <20 ESR (mm/h) >140 WBC (K/uL) 27.6 x [10.sup.3] (PMN %) (92.3%)
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|Author:||Kantorovich, Vitaly; Patil, Naveen; Rassouli, Negah|
|Publication:||Archives: The International Journal of Medicine|
|Article Type:||Case study|
|Date:||Jan 1, 2010|
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