Evaluation of thymic dimensions in patients with multisystem inflammatory syndrome.

Background: Multisystem inflammatory syndrome (MIS-C) is the most important complication of COVID-19 in the pediatric population. Unfortunately, this problem is an unpredictable situation in patients with COVID-19. We aimed to evaluate the effects of MIS-C on thymus dimensions in pediatric patients.

Methods: We retrospectively analyzed the files of 368 pediatric patients aged 2-18 years, who were diagnosed with COVID-19. Computer Tomography (CT) images of 22 patients diagnosed with COVID-19 and 10 patients diagnosed with MIS-C were evaluated in detail by two board-certified radiologists. Eighteen age and sexmatched patients who applied to the emergency department of our hospital for any reason and had a CT scan for any reason were selected as the control group. The data of both groups were statistically compared.

Results: Considering the differences between the groups in terms of laboratory data, monocytes, hemoglobin, and platelet were significantly lower in the MIS-C group than the other groups. Procalcitonin, C- reactive protein, neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and proBNP levels were statistically significantly higher in the MIS-C group compared to the other groups Regarding the differences in thymus dimensions, thymus AP diameter, transverse diameter, length, thickness, and volume were significantly higher in the MIS-C group than in the other groups There was a significant positive correlation between the transverse diameter of the thymus and CRP, procalcitonin, pro-brain natriuretic peptide (proBNP), and NLR levels.

Conclusions: Our study shows that thymus dimensions and acute phase reactants are higher in pediatric patients in the MIS-C group. Also, thymus transverse diameter, thymus thickness, and PLR values pose a risk for the development of MIS-C. More research is needed on the role of the thymus gland in the pathogenesis and diagnosis of MIS-C.