Persistence of Elevated Procalcitonin in a Patient with Coronavirus Disease 2019 Uncovered a Diagnosis of Medullary Thyroid Carcinoma

Abstract

\n Objectives\n During this ongoing pandemic of coronavirus disease 2019 (COVID-19), procalcitonin (PCT) assay has proven to be a useful tool in assisting clinicians to diagnose bacterial superinfection. However, in the absence of signs of infection or at resolution thereof, inappropriately and persistently high PCT may suggest and reveal the presence of other pathologies. We report a patient with acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia in whom persistence of initially elevated PCT during recovery prompted the diagnosis of medullary thyroid cancer (MTC).\n \n Case report\n A 43- year-old man presented with a two-day history of fever, sneezing, sore throat and dry cough. Physical exam revealed decreased sounds and coarse crackles in both lung bases at auscultation. Medical history was positive for cognitive impairment since birth, arterial hypertension, systemic lupus erythematosus with nephritis. Initial studies included mild lymphocytopenia 650/μl (760 – 5000), D-Dimer 0.73 μg/ml (< 0.5), C reactive protein (CRP) of 62 mg/l (< 5) and PCT of 94 ng/ml (0.00 – 0.10). Positivity for SARS-Cov-2 RNA was detected and chest computerized tomography showed bilateral ground-glass opacities in the basilar lung zones and hyperdense and irregular foci in the thoracic vertebral bodies. Empirical antibiotic therapy was started and was maintained for seven days but, despite clinical improvement and the normalization of CRP, serum PCT was persistently high (84 ng/ml). Serum calcitonin (CTN) was 2120 pg/ml (normal up to 12 pg/ml). Neck ultrasound revealed inhomogeneously echogenic lymph nodes with small punctate calcifications and a non-homogeneous thyroid with multiple nodules. Cytological examination by fine needle aspiration and CTN measurement on washing liquid confirmed the suspicion of MTC. The patient underwent total thyroidectomy with bilateral cervical lymph node dissection. Histological analysis confirmed MTC of right thyroid lobe and metastasis at lymph nodes of the central right midneck area. Blood tests performed 48 hours after surgery showed a lowering of CTN (986 pg/mL) and PCT (16 ng/mL). A 6-months follow up showed persistent increased CTN and PCT levels (921 pg/ml and 16 ng/ml, respectively) while a (18)F-fluorodihydro-xyphenylalanine ((18)F-DOPA) PET did not reveal any suspicious fixations at thyroid lodge and cervical lymph node stations while multiple osteoblastic foci in the skeletal area were described. A close follow-up was planned with establishment of the results of RET gene analysis.\n \n Discussion\n Although CTN is the gold standard biochemical parameter for the diagnosis and follow-up of MTC, PCT can be useful as a biochemical marker of MTC suspicion in patients with inflammatory conditions and persistently elevated PCT even after resolution. In the present CASE, high levels of PCT in a patient with Covid-19 pneumonia without signs of bacterial infection, allowed to diagnose MCT.\n \n Conclusion\n In the absence of any other signs of infection, a complete clinical assessment, including neck palpation, CTN measurement and thyroid ultrasound should be performed in the presence of persistently elevated PCT.\n