38-year-old Malaysian builder, previously well, presented with a 2-week history of worsening right neck pain associated with odynophagia, high fevers, weight loss of 6kg and palpitations. His right thyroid lobe was enlarged, firm and tender to palpation.
Investigations showed marked thyrotoxicosis and elevated inflammatory makers. Thyroid ultrasound was consistent with a large nodule or coalescent nodules with features suggestive of recent haemorrhage without evidence of infection. A 99mTc-Thyroid scan showed generalised reduced uptake of 0.7%.
He was treated for suspected subacute thyroiditis (SAT) but failed to improve. A fine needle aspirate (FNA) performed on day-3 drained pus. The diagnosis of acute suppurative thyroiditis (AST) was made and piperacillin/tazobactam was administered for a total of 19days. Cultures grew Streptococcus anginosus and mixed anaerobes with normal histology. Despite initial improvement, he required surgical exploration revealing a multiloculated abscess in the right thyroid lobe and a separate abscess in the right sternomastoid. He became afebrile on day-1 post surgical washout. Extensive investigations into the source of AST revealed no cause.
Discussion
AST is very rare but overlapping clinical features can make it difficult to distinguish from the more common SAT. Moreover, both conditions show reduced 99mTc-Thyroid scan uptake. SAT is a self-limiting condition but AST has a mortality of up to 12% and therefore it is crucial to make a timely diagnosis.
Although ultrasound and CT thyroid may identify a thyroid abscess, findings in the early stages are indistinct. Helpful findings may include fluid around the affected thyroid lobe, heterogenous low-density areas within the thyroid gland and unifocal hypoechoic lesions. Thyroid FNA is diagnostic.
Treatment comprises broad-spectrum antibiotics and drainage by ultrasound-guided FNA or by surgical washout.
Pyriform sinus is a common cause of left recurrent AST. Other causes include lymphatic or haematogenous spread, neck trauma and ruptured oesophagus among others.