Lung cancer is one of the most fatal types of cancer and paraneoplastic syndromes are commonly associated with lung cancer. Paraneoplastic Cushing can be associated with different types of tumors, especially small cell lung cancer (SCLC). The aim of this report was to describe the status of a patient presenting with progressive weakness, who did not have a previous medical history. Clinical examination revealed bilateral edema of the lower limbs. Lab results exhibited severe hypokalemia and metabolic alkalosis. physical examination showed elevated blood pressure. Imaging revealed a large mass with necrosis. Bronchoscopy was done and biopsy pathology showed SCLC. The patient underwent chemotherapy with cisplatin and etoposide. Following SCLC, the patient developed a type of paraneoplastic syndrome called Cushing syndrome. He experienced a severe decrease in saturation in the second session of chemotherapy and eventually died. With respect to the fact that most paraneoplastic syndromes are associated with poor response to treatment, high clinical suspicion is essential for the rapid diagnosis of these syndromes to improve outcomes.