Serum Mammalian Target of Rapamycin (mTOR) Levels in Patients with Post-COVID-19 Fibrotic-like Lung Changes: A Cross-Sectional Study

<b>Background/Objectives:</b> Post-COVID-19 fibrotic-like lung changes (PC19-FLC), which may represent persistent post-inflammatory abnormalities or early fibrotic remodeling, have emerged as an important long-term pulmonary sequela following SARS-CoV-2 infection. However, the underlying pathogenic mechanisms remain incompletely understood. This study aimed to investigate the potential association between mammalian target of rapamycin (mTOR) activity and the presence of PC19-FLC. <b>Methods:</b> This single-center, cross-sectional study included 70 patients who met the predefined inclusion criteria. Participants were categorized according to the presence or absence of PC19-FLC on chest computed tomography. Demographic, laboratory, and radiological data were collected. Serum mTOR levels were measured using enzyme-linked immunosorbent assay (ELISA). <b>Results:</b> Serum mTOR levels and modified Medical Research Council (mMRC) dyspnea scores were significantly higher in patients with PC19-FLC compared with those without fibrotic-like changes. Receiver operating characteristic (ROC) curve analysis identified a serum mTOR cut-off value of 6.15 ng/mL (sensitivity 83%, specificity 94%) for discriminating patients with PC19-FLC in this cohort. Serum mTOR levels were significantly correlated with forced vital capacity (FVC%), mMRC dyspnea score, and peripheral oxygen saturation (SpO₂). <b>Conclusions:</b> Increased serum mTOR levels were associated with the presence of fibrotic-like lung changes after COVID-19 and may help distinguish patients with such CT abnormalities in this cohort. Higher mTOR levels were also associated with greater dyspnea severity, lower lung volumes, and reduced peripheral oxygen saturation. These findings suggest a potential role of mTOR signaling in post-COVID-19 pulmonary sequelae and warrant further investigation in larger, multicenter studies.