Although the syndrome of inappropriate
antidiuretic hormone secretion (
SIADH) is commonly associated with many lung conditions and drugs used for treating them, no literature describes a direct association between
SIADH and
interstitial lung disease. This case report discusses a 79-year-old male patient who presented to the emergency department (ED) with altered mental status following a fall. The patient had clinical symptoms and imaging findings concerning
interstitial lung disease (ILD), and laboratory tests from the ER indicated severe
hyponatremia and an increased white blood cell count, suggesting an unusual clinical picture. Detailed workup and
medication reconciliation revealed no other medical conditions or intake of drugs associated with
SIADH; however, the patient's low serum osmolality, high urine osmolality, high urine
sodium, and improvement in serum
sodium level with the initiation of
0.9% saline,
salt tablets, and
tolvaptan verify the presence of
SIADH. While the association between
SIADH and ILD is not well documented in medical literature, a few case reports from different regions have indicated a potential link, either through
drug-induced ILD or
SIADH resolution coinciding with ILD improvement. Hence, we describe a case of idiopathic
SIADH, possibly associated with
interstitial lung disease. This case demonstrates the importance of recognizing the coexistence of
SIADH and ILD, as severe
hyponatremia can lead to potential life-threatening neurological consequences.