Published online Jul 16, 2022. doi: 10.12998/wjcc.v10.i20.7171
Peer-review started: February 4, 2022
First decision: March 23, 2022
Revised: April 13, 2022
Accepted: May 17, 2022
Article in press: May 17, 2022
Published online: July 16, 2022
Procalcitonin (Pct) is a common biomarker in clinical practice, especially in the era of coronavirus disease 2019 (COVID-19) infection. Although it is frequently used for the diagnosis and prognostication of bacterial infections or sepsis, it is also elevated in a few other conditions, including medullary thyroid carcinoma (MTC).
A 43-year-old female presented with moderately severe COVID-19 pneumonia in April 2021. She gradually recovered clinically; however, despite normalization of other inflammatory markers, Pct levels remained persistently elevated. Further workup identified the cause as left lobe MTC with locoregional metastasis. Calcitonin levels were high, and carcinoembryonic antigen levels were normal. The patient underwent total thyroidectomy and neck dissection, which was followed by another radical neck dissection due to residual disease. Currently, she is doing well, nearly having completed her course of external beam radiotherapy with no recurrence. Pct is well documented as a screening tool for MTC, especially because of its stable nature compared to calcitonin in the community settings. It is important to keep in mind the differential diagnosis of MTC in patients with persistently elevated Pct levels despite normal levels of other acute phase reactants. To the best of our knowledge, this is the first report from Asia of such an incidental diagnosis of MTC due to persistently elevated Pct levels in a patient with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
Persistently elevated Pct levels can occur in any pro-inflammatory state including infections, sepsis, or acute respiratory distress syndrome. In the current setting, SARS-CoV-2 infection is one such clinical scenario, and in rare situations of persistent elevation, MTC may need to be ruled out.
Core Tip: Procalcitonin (Pct) is a biomarker used very commonly for infections in our clinical practice. It is routinely used in coronavirus disease 2019-infected patients. In this setting, persistent Pct elevation despite normalization of other inflammatory markers may present a diagnostic dilemma. This case highlights the importance of identifying occult medullary thyroid carcinoma in such situations, which would otherwise have been missed and left untreated. In our patient, this led to proper treatment and a successful outcome.