Small cell lung cancer progressing into fatal ascending motor and sensory polyneuropathy despite dramatic response to chemotherapy: A case report.

rationaleParaneoplastic syndromes occur in 10% to 20% of all malignancies, with paraneoplastic neurological syndromes in less than 1% of all malignancies. In small cell lung cancer (SCLC), paraneoplastic manifestations are more common, affecting up to 5% of cases. Common manifestations include syndrome of inappropriate antidiuretic hormone secretion, Cushing's syndrome due to adrenocorticotropic hormone secretion, paraneoplastic cerebellar degeneration, and Lambert-Eaton myasthenic syndrome. Paraneoplastic acute motor and sensory polyneuropathy is an exceptionally rare but severe complication, necessitating timely diagnosis and management. PATIENT CONCERNS: A 55-year-old male with an 80 pack-year history of smoking presents to the hospital with a 3-week history of fevers, productive cough, dyspnoea, and wheeze. He had no significant comorbidities. DIAGNOSES: Extensive radiological investigations revealed a large mass at the right hilum compressing on the right lower bronchus with metastatic adrenal deposits. Biochemical investigations confirmed syndrome of inappropriate antidiuretic hormone secretion, and histology identified SCLC.

interventionsDespite initiating a combination chemotherapy with carboplatin and etoposide, the patient developed progressive motor paralysis and sensory loss over 4 days, leading to a diagnosis of paraneoplastic acute motor and sensory polyneuropathy. OUTCOMES: He deteriorated rapidly and died 14 days after symptom onset due to respiratory failure, underscoring the aggressive nature of paraneoplastic syndromes. LESSONS: Paraneoplastic syndromes, particularly in SCLC, pose significant diagnostic and therapeutic challenges. This case highlights the importance of early recognition and prompt multidisciplinary intervention, which may improve outcomes despite the low incidence of these severe complications. Treating cancer with appropriate systemic chemotherapy or suppression of the immune response alleviates neurological symptoms and improves prognosis.