Subacute De Quervain thyroiditis after SARS-CoV-2 infection

COVID-19 (COronaVIrus Disease 2019), caused by the SARS-CoV-2 virus, is currently a pandemic affecting millions of people around the world. Cases of autoimmune thyroid disease¹ and subacute thyroiditis^2–4 associated with SARS-CoV-2 infection have been reported. We report a case of subacute thyroiditis in our setting following asymptomatic SARS-CoV-2 infection.

A 46-year-old woman with no personal or family history of interest and no ongoing treatment was seen at an endocrinology clinic due to pain in the thyroid area for the previous two months. The pain, which worsened with swallowing and neck movements, started in the right thyroid area, radiated to the right ear and, a month later, spread to the left thyroid lobe and left ear. This was accompanied by a low-grade fever, malaise and insomnia. She had no signs or symptoms of thyrotoxicosis. Examination revealed a grade 1 goitre with significant pain on palpation. The patient provided the results of laboratory testing ordered by her general practitioner that showed hyperthyroidism, with thyroid-stimulating hormone (TSH) levels of 0.11 µIU/ml (0.55–4.78), free T4 levels of 2.18 ng/dl (0.89–1.76), an erythrocyte sedimentation rate (ESR) of 68 mm/h and mild positivity for thyroperoxidase antibodies (TPO Ab), as well as a negative polymerase chain reaction (PCR) test for SARS-CoV-2 infection. She had started treatment with non-steroidal anti-inflammatory drugs (NSAIDs) with partial improvement in her symptoms.

As subacute thyroiditis was suspected, oral prednisone (40 mg per day on a down-titration regimen for six weeks) and further hormone testing with autoimmunity, thyroid ultrasound and thyroid scintigraphy were ordered.

Two weeks later, the patient showed significant clinical improvement in her thyroid function (TSH levels of 0.018 µIU/ml and free T4 levels of 1.68 ng/dl), an ESR of 23 mm/h, C-reactive protein levels of 1.3 mg/dl (0–1) and negativity for TSH receptor Ab. Neck ultrasound revealed a heterogeneous enlarged thyroid gland with normal vascularisation and a heterogeneous, hypoechogenic left thyroid nodule measuring 15 mm × 30 mm, with no cervical lymphadenopathy. Thyroid scintigraphy showed overall hypouptake of the radioactive tracer, consistent with the clinical suspicion of thyroiditis. The patient presented another negative PCR test for SARS-CoV-2.

She was kept on a down-titration regimen of prednisone, and a fine needle aspiration biopsy (FNAB) of the thyroid nodule; further hormone testing; and, in light of case reports of subacute thyroiditis after COVID-19, serology for SARS-CoV-2 were ordered. At her monthly check-up, the patient showed resolution of her signs and symptoms. Laboratory testing revealed mild thyroid hypofunction (TSH 7.75; free T4 0.66), normal C-reactive protein levels and a normal ESR. The FNAB was insufficient for diagnosis. The serology for SARS-CoV-2 showed positivity for IgG, thus confirming past COVID-19. Another FNAB was ordered, but a follow-up ultrasound did not show any thyroid nodule; it only showed areas of focal hypoechogenicity, with no nodules that could be delimited. The patient's thyroid function returned to normal within three months.

Subacute granulomatous thyroiditis, or De Quervain’s thyroiditis, is a thyroid inflammatory disease of probable viral origin (direct infection or a post-viral inflammatory reaction in genetically predisposed individuals). It has been most often linked to enterovirus, adenovirus, Coxsackievirus and measles virus infections as well as parathyroiditis.⁵ Our patient, previously asymptomatic, developed signs and symptoms typical of subacute thyroiditis two months after the COVID-19 pandemic was declared, but did not seek care until two months after the onset of her symptoms. Additional testing and her clinical course supported the diagnosis of subacute thyroiditis, and serology confirmed past COVID-19; active infection was ruled out on two occasions in the course of her clinical follow-up. Our case offers evidence on the relationship between SARS-CoV-2 and subacute thyroiditis. According to the latest report prepared by the Red Nacional de Vigilancia Epidemiológica [Spanish National Epidemiological Surveillance Network],⁶ 50.6% of patients with COVID-19 detected as of 10 May 2020 have been asymptomatic. Hence, given the non-negligible percentage of patients who do not show symptoms, we believe that patients with signs and symptoms consistent with subacute thyroiditis must be assessed for possible past COVID-19.