A Seizure That Has Started in the Lungs: Unusual Presentation of Lung Cancer

Abstract

It is hardly surprising that paraneoplastic syndrome could be the first sign of an underlying malignancy. Sometimes, a patient’s condition is not apparent clinically but is revealed through laboratory findings, as they may appear clinically well while being biochemically unwell, such as in patients with the Syndrome of Inappropriate Anti-Diuretic Hormone Secretion (SIADH). This case report highlights SIADH and Small-Cell Lung Cancer (SCLC) as a classic clinical pairing in elderly smokers. It presents a 64-year-old Saudi male who was brought to the emergency department after experiencing new-onset generalized tonic-clonic seizures, despite having no prior history of epilepsy or any identifiable triggers for his symptoms. Laboratory workup revealed severe hyponatremia, with the patient being euvolemic on examination of his volume status, fulfilling the criteria for the textbook definition of SIADH. Management included cautious correction of his serum sodium levels using hypertonic saline boluses and fluid restriction. After stabilization, lung cancer was suspected based on chest CT imaging and later confirmed via lung biopsy. He was subsequently referred to a tertiary center for ongoing management of hyponatremia and definitive treatment of lung cancer.