Red flag conditions:Initial evaluation ruled out acute cardiovascular events (normal cardiac workup) and severe infection (negative CRP/PCT). However, physical examination revealed anterior thoracic mass, laboratory findings revealed mild anemia (Hb 91 g/L), hyperglobulinemia (Glb 76.18 g/L), hypoalbuminemia (Alb 27.94 g/L), and elevated ESR (137.68 mm/h). These abnormalities raised concern for occult malignancy, particularly cancer-related fatigue (CRF). The gene discussed is GSTM1; the disease is anemia.