Longitudinal Trajectories of Inflammatory, Immune, and Coagulation Biomarkers in Critical COVID-19 Under Chronic Etanercept Therapy: A Case Report

Background: Severe COVID-19 is driven by a complex interplay between systemic hyperinflammation, cellular immune dysregulation, and activation of coagulation cascades. Case Presentation: We report the case of a 52-year-old man with a history of rheumatoid arthritis and psoriasis managed with chronic etanercept therapy, who was hospitalized with rapidly progressive COVID-19. Longitudinal monitoring of C-reactive protein (CRP), interleukin-6 (IL-6), soluble interleukin-2 receptor (sIL-2R), neutrophil-to-lymphocyte ratio (NLR), D-dimer, and fibrinogen demonstrated a transient suppression of select acute-phase reactants followed by profound cellular immune dysregulation and escalating thrombo-inflammatory activity. Despite multimodal management—including remdesivir, convalescent plasma, invasive mechanical ventilation, and veno-venous extracorporeal membrane oxygenation (ECMO)—the patient suffered fatal cardiac arrest. Conclusions: This case highlights the clinical utility of longitudinal, multiparametric biomarker profiling in severe COVID-19 and underscores the critical importance of timely immunomodulatory interventions prior to irreversible immunothrombotic damage.