A 62-year-old man with past medical history of benign prostate hyperplasia, congestive heart failure, and hyperlipidemia presents to his primary care physician for a routine follow-up visit. Today, he complains of progressively worsening fatigue and back pain for the past 4 weeks. He states that there are days that he feels so tired that he does not leave the house. He no longer enjoys playing golf or fishing on the weekends. On physical examination, his temperature is 37.2°C, blood pressure is 134/72 mm Hg, pulse rate is 74 beats/min, and respiratory rate is 12 breaths/min. Pallor conjunctiva and point tenderness are noted over his lumbar spine. The rest of the physical examination is unremarkable. His medications include pravastatin, furosemide, and tamsulosin. He also has been taking aspirin daily for his back pain. Laboratory data show the following:
What is the MOST likely cause for the patient’s acid-base disturbance?A. Starvation ketoacidosis
Correct Answer: D
Based on the patient’s symptoms of fatigue and back pain, along with laboratory studies, including anemia and hypoalbuminemia, the patient most likely has multiple myeloma (MM). Patients with MM also commonly have hypoalbuminemia for which a correction factor needs to be applied. For any 1 g/L decrease of albumin, the anion gap increases by 2.5. So, while the anion gap without albumin is normal at 11, after correction factor for albumin, the anion gap is >12.
Corrected anion gap (AG) = AG + 2.5 × (4.5 − measured albumin [g/dL]) When calculating the anion gap, attention should be paid to patients with hypoalbuminemia and hypophosphatemia as this will increase the anion gap further.