A 63-year-old male with weight loss, fever, dyspnea, and rash

On a hot, humid summer day, a 66-year-old male with complaints of anorexia, weight loss, flu-like symptoms, shortness of breath, and rash is brought to your office by his son. His fever, which began last evening, has been recurring since shortly after he moved to this locale to be near his son and grandchildren about 10 months ago. While the patient is at his son’s home, in the company of his grandchildren, he seems to improve; yet when the patient returns to his home, he becomes ill. The son mentions that his father generally has been withdrawn and housebound since he broke his hip a year ago. The patient lives in a log cabin that has only natural ventilation and is heated by a wood stove.

Physical examination reveals a well-nourished male, sweating profusely and mildly tachypneic. He exhibits confusion and is oriented to person only. His blood pressure is 132/70 sitting, pulse 120/minute and regular, respiratory rate 24/minute and shallow without stridor. He has a rectal temperature 104.7°F. He has no cough and no vomiting or diarrhea. The skin is warm and moist; the mucous membranes are wet. There is a papular erythematous rash on the forearms bilaterally and on the neck. There is no skin discoloration, acne, or conjunctivitis. There are no focal neurologic findings, including no Kernig’s or Brudzinski’s signs. The lungs are clear to auscultation and percussion. There is no costovertebral tenderness. Bowel sounds are normal, and the remainder of the abdominal examination is unremarkable. You admit the patient to the hospital.

Further history reveals that the patient is a retired botanist. He had been active and generally well before the fall in which he fractured his hip. He is being treated for mild hypertension with a diuretic. There is no other significant medical or surgical history. For the past 6 months, the patient has been taking amitriptyline for depression as prescribed by his former personal physician, and he has been treating his flu-like symptoms with aspirin at the recommended over-the-counter doses. He is using calamine lotion daily on the rash. He admits to being generally withdrawn and home-bound but denies any thoughts of suicide.

Initial laboratory values show a serum pH of 7.39, Paco₂ 21 and Pao₂ 120 on 2 liters of oxygen. Serum electrolytes reveal the following: sodium 131 mEq/L (normal 135–148); potassium 5.1 mEq/L (normal 3.5–5.3); chloride 83 mEq/L (normal 95–105); and bicarbonate 21 mEq/L (normal 22–28). The anion gap is 32. Blood urea nitrogen is 32 mg/dL (normal 5–20) and creatinine 2.8 mg/dL (normal 0.7–1.5). The urinalysis is normal; urine pH is 5.5. Initial white blood count is 11.7×10³/mm³ (normal 4.5–11×10³) with 61% neutrophils (normal 60%); the spun hematocrit is 47% (normal 42%–52%). Blood salicylate level of 5 mg/dL is within the therapeutic range.

Answers to the Pretest questions are on page 14.