A 78-year-old female patient presented to the emergency room with dry cough, mild dysphagia, rapidly growing neck swelling, neck pain and soft tissue haematoma on the right side of the neck and upper thorax. Lab showed mild leukocytosis, otherwise unremarkable. No history of fever, thyroid disease, previous surgery or trauma.
Computed tomography (CT) was performed showing the enlargement of the right thyroid lobe, its heterogeneity with several minor indistinct hypodensities (Fig.1,2). There was massive inflammatory infiltration of locoregional fatty tissues, with significant compression on larynx, trachea and hypopharynx (Fig 2,3). No encapsulated fluid collections were noted. There were signs of cervical lymphadenopathy and mediastinitis. Right paraesophageal mass was defined as ddx lymphnodes’conglomerate (Fig 3,4,5).
Barium swallow (BS) was additionally done to confirm or exclude the presence of pyriform sinus fistula, after 1 month of therapy. It could not be done initially due to patient’s status. BS showed retention of a small amount of contrast in the right vallecula (Fig 6.) and a minor extraluminal compression on the right side of the cervical oesophagus (at the level of VC4-VC6) (Fig.7) which is most probably due to earlier mentioned lymph node's conglomerate.
Dedicated US- FNA confirmed colloid nodules in enlarged right thyroid lobe.
Background: Thyroid gland is rarely infected because of its complete fibrous encapsulation, rich vascular and lymphatic supply, and biochemically high iodine concentration.  In adults, routs of infection are predominantly hematogenous or lymphatic spread or by iatrogenic infection after fine-needle aspiration biopsy. Pre-existing thyroid disorders have a greater predisposition for acute suppurative thyroiditis (AST). In children, AST ofter occurs due to congenital anatomic defects as third or fourth branchial arch anomalies. 
Clinical Perspective: Onset of AST is generally sudden and the clinical picture progresses rapidly.  Fever, neck pain, dysphagia and a swollen mass over the lobe of the thyroid gland, increased C-reactive protein, measurable thyroglobulin are features of this illness.  Our patient did not have a fever, but was symptomatic for other distinctive signs. Thyroid hormones were at the reference level though. When the possibility of AST is considered in differential diagnosis, a CT scan should be performed. It can confirm or alter the clinical impression and aid in initiating early therapy. 
Imaging perspective: CT with intravenous contrast of the neck and chest mapps the process more accurately, graphically demonstrates the thyroid’s involvement, estimates the overall iodine content of the thyroid gland and offers an anatomic assessment of soft tissue enhancement and abscess extension into the neck or mediastinum. 
US and US-FNA biopsy are the best diagnostics and therapeutic option if the CT reveals a thyroid mass or fluid collection.  Follow-up barium swallow is indicated to identify the presence of a fistula. 
Outcome: Treatment of acute infectious thyroiditis (AIT) involves antibiotic therapy based on antibiogram. Empirical broad-spectrum antimicrobial treatment provides preliminary coverage for a variety of bacteria, incl. S. Aureus and S. Pyogenes. Early treatment of AIT prevents further complications, as it was with this case. The patient recovered fully after systemic antibiotic therapy. However, if antibiotic treatment does not manage the infection, surgical drainage is required (US/CT detection of an abscess or gas formation). Another treatment of AIT involves surgically removing the fistula (mainly in children). [8,9]
Acute suppurative thyroiditis is an extremely rare disease in the adult thyroid.
US and US-FNA biopsy are the best diagnostics and therapeutic option if the CT reveals a thyroid mass or fluid collection.
Prognosis is favourable in patients who are immunocompetent and who does not have branchial arch anomalies or a pyriform sinus fistula.
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