Severe Symptomatic Hyponatremia Caused by Low Dose Oral Cyclophosphamide: A Case Report

Cyclophosphamide (CY), an alkylating agent, is frequently used in the treatment of various autoimmune disorders and malignancies. Acute hyponatremia is a well-known side effect of moderate to high dose intravenous CY treatment, but is rare in patients treated with low dose intravenous CY. We report the case of a severe symptomatic hyponatremia in a 68-year-old woman with renal impairment who was treated with oral CY (100 mg/day) for anti-neutrophil cytoplasmic antibody (ANCA) associated glomerulonephritis (GN). This case demonstrates that even oral CY could be associated with life threatening acute hyponatremia and should be used with caution.