Hi Group 5:

here we have a 65-year-old white woman with small cell lung cancer has increasing confusion and lethargy over the past week. She is afebrile and normotensive, and she has no edema or jugular venous distention. She is lethargic but is able to move her extremities without apparent motor deficits, and her deep tendon reflexes are decreased symmetrically. Her serum sodium level is 108 mmol/L, potassium 3.8 mmol/L. bicarbonate 24 mEq/L, blood urea nitrogen (BUN) 5 mg/dL, and creatinine 0.5 mg/dL; serum osmolality is 220 mOsm/kg, and urine osmolality is 400 mOsm/kg. A CT scan of the brain shows no masses or hydrocephalus.

You picked up on all the right cues and clues and nailed the dx of Coma/lethargy secondary to severe hyponatremia, which is most likely caused by a tumor-related syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Well done!

Jack