Subacute Thyroiditis After SARS-CoV-2 Infection Presenting With Pyrexia of Unknown Origin

Subacute thyroiditis(SAT) is associated with viral(destructive) or post-viral(inflammatory) origin.[1]The most common clinical characteristics of SAT are female sex preponderance, anterior neck pain and fever.[2,3] Heart rhythm disorders and silent cervical forms have been described in SAT associated with SARS-CoV-2 infection,which occurs 16 to 36 days after resolution of COVID-19.[1,3] Symptomatic improvement occurs in a few days after initiation of therapy with sterods or NSAID.[3] Pyrexia of Unknown Origin (PUO) is a very rare presentation of SAT.[2] Hereby, a case of SAT, presenting with painful neck swelling and persistent fever (5weeks duration), two weeks after resolution of COVID-19, is being discussed. The index patient was a 50-year old obese,normotensive, diabetic (10 years duration, HbA1c-6.6% on SU, metformin, sitagliptin and dapagliflozin) male. TSH was suppressed (0.02 mIU/L), FT4 (3.06 ng/dl, upper limit of normal-1.48ng/dl) and FT3 (3.9 pg/ml, upper limit of normal-3.71 pg/ml) were elevated. Total T4 and T3 were normal. HS-CRP was markedly elevated. IL-6 and TBG were not estimated. Cervical USG revealed diffuse hypoechogenecity of thyroid gland and thyromegaly. There was reduced uptake in thyroid scan (technetium). The patient became afebrile after 4 days of initiation of 30 mg prednisolone (tapered by 10 mg every 5 days). The initial tachycardia reverted to sinus rhythm with marked reduction of neck tenderness. This case highlights certain considerations for SAT associated with SARS-CoV-2 infection. Firstly, it can present with PUO (first case report). Secondly, it may be associated with normal total T4 and T3 which can happen due to reduced TBG consequent upon increased IL-6.[4] References: 1. Caron Philippe: Thyroid disorders and SARS-CoV-2 infection: From pathophysiological mechanism to patient management. Ann Endocrinol (Paris), 2020, Sept. 2. Fever of Unknown Origin as a Sole Presentation of Subacute Throiditis in an Elderly Patient. A Case Report with Literature Review. Raj R, Yada S, Jacob A et al: Hindawi Case Reports in Endocrinology, 2018, Article ID 5041724 3. Brancatella A, Ricci D, Latrofa F et al: Is subacute thyroidits an underestimated manifestation of SARS-CoV-2 infection? Insights from a case serie. J Clin Endocrinol Metab, 2020, Aug 11, dgaa537. 4. Bartaleno L, Brogioni S, Grasso L and Martino E: Increased serum interleukin-6 concentration in patients with subacute thyroiditis:relationship with concomitant changes in serum T4-binding globulin concentration. Journal of Endocrinological Investigation, 1993, 16, 213-218.