This week's free board review question...
A 58-year-old man presents to you with confusion. He and his family emigrated from West Africa 6 months ago. His wife indicates that he has had a nonproductive cough, poor appetite, and a 50-pound unintentional weight loss over this time.
His vital signs are as follows: blood pressure 96/70 mm Hg, heart rate 110 beats/minute, respiratory rate 18 breaths/minute, and temperature 100.2 °F (37.9 °C). He is disheveled, awake, and responsive, but he is disoriented to time and place. No neurologic findings are evident. Skin turgor is normal and there is no pigmentation. His lungs are clear. Abdominal examination reveals an enlarged spleen. There are multiple, nontender, movable lymph nodes in the cervical area bilaterally.
Laboratory results show:
Purified protein derivative (PPD): 16-mm induration
White blood cell count: 12,800/mm3 with no shift of neutrophils
Serum transaminase: 75U/L
Serum sodium: 123 mEq/L
HIV test: Positive
You obtain an x-ray of his chest (see Figure), the findings of which reveal 3-mm micronodular lesions throughout both of his lungs.
What is the most likely explanation for the low serum sodium level in this patient?
syndrome of inappropriate antidiuretic hormone secretion (SIADH)
psychogenic water drinking
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