Hyponatremia associated with primary central nervous system lymphoma

Excerpt

An 80-year-old man was admitted to the emergency department with general weakness. On admission, his blood pressure was 140/70 mmHg; body temperature, 36.5 °C; pulse rate, 78 beats/min; and respiration rate, 20 breath cycles/min. He was not dehydrated, and did not have edema. The chest radiograph did not show any active lung lesions. The laboratory data were as follows: white blood cell count, 7,500/mm³; hemoglobin, 11.0 g/dL; platelet count, 193,000/mm³; blood urea nitrogen, 33.6 mg/dL; serum creatinine, 1.2 mg/dL; glucose, 126 mg/dL; sodium, 116 mEq/L; potassium, 4.6 mEq/L; chloride, 93 mEq/L; uric acid, 2.7 mg/dL; and serum osmolality, 249 mosmol/kg. There was no abnormal finding on random urinalysis. Urine sodium concentration was 116 mEq/L, and urine potassium concentration was 25.9 mEq/L. Urine osmolality was 592 mosmol/kg. Results of endocrine function tests were as follows: T3, 0.23 ng/mL (reference range, 0.6–1.6 ng/mL); free T4, 0.68 ng/dL (reference range, 0.8–1.54 ng/dL); thyroid-stimulating hormone, 0.155 μU/mL (reference range, 0.55–4.78 μU/mL); cortisol, 2.3 μg/dL (reference range, 3.0–23.0 μg/dL); adrenocorticotropic hormone 13.0 pg/mL (reference range, 6.0–76.0 pg/mL); growth hormone, 0.1 ng/mL (reference range, 0.5–17.0 ng/mL); prolactin, 49.7 ng/mL (reference range, 2.8–29.9 ng/mL); luteinizing hormone, 0.12 U/L (reference range, 3.1–34.6 U/L); follicle-stimulating hormone, 1.11 U/L (reference range, 1.4–18.1 U/L); and free testosterone, 0.08 pg/mL (reference range, 5.6–19.0 pg/mL). Brain magnetic resonance imaging revealed abnormal contrast-enhancing lesions in the hypothalamus, pituitary stalk, optic chiasm, and lateral ventricles of both sides (Fig. 1). Endoscopic brain biopsy was performed.

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