# Syndrome of Inappropriate Anti-diuretic Hormone (SIADH) in Non-small Cell Lung Cancer (NSCLC) Following Agent Orange Exposure: A Case Report

## TL;DR

A 77-year-old man with a history of Agent Orange exposure and smoking developed SIADH linked to non-small cell lung cancer.

## Contribution

This case report highlights a rare occurrence of SIADH associated with NSCLC following Agent Orange exposure.

## Key findings

- The patient exhibited SIADH symptoms consistent with malignancy, later confirmed as non-small cell lung cancer.
- Pleural effusion and hyponatremia were key clinical features leading to the diagnosis of SIADH.
- The case underscores the importance of considering paraneoplastic syndromes in patients with atypical hyponatremia.

## Abstract

We present the case of a 77-year-old male with a significant smoking history and prior Agent Orange exposure, who was admitted to the hospital multiple times with clinical and laboratory findings consistent with the syndrome of inappropriate anti-diuretic hormone (SIADH). The patient presented to the hospital on multiple occasions with symptoms and laboratory findings supportive of SIADH in the setting of malignancy. During his first visit, imaging studies demonstrated a right-sided pleural effusion, which was drained and sent for cytology and immunohistochemical staining studies. Following correction of his presenting hyponatremia, he was discharged with appropriate medications and follow-ups to discuss pleural fluid results. Three weeks later, he presented with similar symptoms, and the available pathology results of the pleural fluid specimen supported non-small cell lung cancer (NSCLC), likely adenocarcinoma.

This report highlights a rare occurrence of SIADH in the setting of NSCLC and emphasizes the importance of considering atypical paraneoplastic syndrome presentations in patients with multifactorial hyponatremia. It also engages in a discussion of the pathophysiology, clinical presentation, and diagnostic approach to SIADH in the context of NSCLC.