FRI563 Subacute Thyroiditis Is An Uncommon Cause Of Pyrexia Of Unknown Origin

Abstract

Abstract Disclosure: N. Luke: None. D. Tay: None. Introduction: Subacute thyroiditis is a rare self-limiting inflammatory thyroid disorder often follows a viral infection. It is a diagnosis that is made clinically when patients present with typical features of anterior neck pain and thyrotoxic symptoms. We share our experience in unraveling a diagnostic challenge of a patient with an atypical presentation of subacute thyroiditis presenting with pyrexia of unknown origin during the Covid 19 pandemic. Clinical case: A 29 years old previously healthy Burmese domestic helper was admitted to a hospital in Singapore for persistent fever of 2 weeks duration associated with persistent sore throat. She had a brief 3 days duration of cough at the onset of fever with no other localizing infective symptoms. She had a booster dose of COVID 19 Moderna vaccination 6 months prior to her presentation with 2 preceding doses of Pfizer-BioNtech vaccine 12 months prior. She was empirically treated for acute pharyngitis with a course of intravenous antibiotics without improvement of her fever. Extensive workup for the fever was performed. A complete blood count showed monocytosis. Blood and urine cultures, urinalysis, COVID polymerase chain reaction (PCR), CMV, EBV, and HIV testing were negative. Respiratory multiplex PCR was negative for adenovirus, coronavirus, influenza, parainfluenza, respiratory syncytial virus, metapneumovirus, rhinovirus, chlamydia, mycoplasma, and Bordetella. CT of the thorax, abdomen, and pelvis was normal. She denied heat intolerance, weight loss, diarrhea, palpitations, or hand tremors. Clinical examination revealed mild anterior neck tenderness but no thyrotoxic features. There were no signs of Graves ophthalmopathy or pre-tibial myxoedema. Thyroid function tests were performed in view of persistent tachycardia which showed elevated free T4 at 51.6 pmol/L (12.7-20.3) with suppressed TSH <0.005 mIU/L (0.3-4.2). TSH receptor stimulating antibody levels (TRab) was elevated at 5.23IU/L (<1.76) and ESR was markedly elevated (115 mm/hr). Thyroid ultrasound showed homogeneous thyroid echotexture with no discrete suspicious nodules or abnormal vascularity. She was started on non-steroidal anti-inflammatory drug (Etoricoxib) with resolution of her fever and neck pain Clinical lesson: Clinicians should be aware that subacute thyroiditis can be a rare cause of pyrexia of unknown origin even in the absence of typical features. Presentation: Friday, June 16, 2023