SHM Converge Scientific Abstract ePoster Gallery-Methotrexate- Induced Hyponatremia in Leptomeningeal Carcinomatosis

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This case report describes a patient with triple-negative breast cancer and leptomeningeal carcinomatosis who developed severe hyponatremia after receiving high-dose systemic methotrexate because she refused intrathecal therapy. Methotrexate is commonly used to treat leptomeningeal disease, especially in breast cancer and hematologic malignancies, and high-dose methotrexate with leucovorin is an accepted alternative when intrathecal treatment cannot be given.<br /><br />The patient had hypertension and a history of brain aneurysms, and her leptomeningeal disease had been confirmed by positive CSF cytology and MRI findings. On day 1 she received methotrexate. By day 5 she developed drowsiness, headache, slurred speech, and word-finding difficulty. CT head showed no new hemorrhage or acute process. She was found to have abrupt hypotonic euvolemic hyponatremia, with sodium falling from 135 to 118 mEq/L. Urine studies showed high urine osmolality (512) and high urine sodium (191), which supported SIADH physiology.<br /><br />Other common causes of euvolemic hyponatremia were excluded, including hyperglycemia, hypothyroidism, and glucocorticoid deficiency. No other medications were felt to explain the sodium drop, and the degree of hyponatremia was too severe to be explained by IV fluids alone. She was treated with hypertonic saline, and her sodium gradually corrected to 135 mEq/L over 48 hours, with return of mental status to baseline.<br /><br />The authors conclude that methotrexate likely triggered SIADH, possibly by increasing arginine vasopressin secretion and causing water retention. They emphasize that although methotrexate-induced hyponatremia is uncommon, it should be considered in patients receiving high-dose methotrexate so that prompt recognition and treatment can improve outcomes.

Asset Subtitle

Shivani Shah

Meta Tag

Author List Aaisha Shah, Dulabh Monga, Pragnan Kancharla, Shivani Shah

Category Clinical Vignettes

Concept Methotrexate

Concept Hyponatremia

Concept Syndrome of Inappropriate Antidiuretic Hormone Secretion

Concept Sodium Level

Concept Carcinomatous Meningitis

Distinguished Non-Finalist

Presenter Organization Allegheny General Hospital

Presenting Author Shivani Shah

Track Adult

Keywords

triple-negative breast cancer

leptomeningeal carcinomatosis

high-dose methotrexate

hyponatremia

SIADH

euvolemic hyponatremia

hypertonic saline

leucovorin

CSF cytology

arginine vasopressin

Methotrexate

Hyponatremia

Syndrome of Inappropriate Antidiuretic Hormone Secretion

Sodium Level

Carcinomatous Meningitis