Kaplan USMLE Step 2: Woman with pain in her mid-back

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.  

A 72-year-old woman comes to the physician because of a three-day history of mid-back pain. She denies any trauma to the back. Examination shows point tenderness over the T8 vertebra.

Laboratory studies show:

• Hemoglobin: 13 g/dL.
• Na⁺: 137 mEq/L.
• Cl^–: 101 mEq/L.
• K⁺: 4.3 mEq/L.
• HCO₃^–: 25 mEq/L.
• Urea nitrogen (BUN): 21 mg/dL.
• Creatinine: 0.71 mg/dL.
• Albumin: 3.6 g/dL.
• Ca⁺: 9.0 mg/dL.
• Alkaline phosphatase: 50 U/L.

X-ray of the spine shows a compression fracture of the T8 vertebral body. Dual energy x-ray absorptiometry (DEXA) shows a bone mineral density T-score of -2.7.

Which of the following is the most likely diagnosis?

A. Metastatic disease.

B. Multiple myeloma.

C. Osteomalacia.

D. Osteopenia.

E. Osteoporosis.

The correct answer is E.

In this patient—a 72-year-old female with an acute, atraumatic thoracic vertebral compression fracture confirmed on X-ray, with a T-score of -2.7 on her DEXA scan—the most likely diagnosis is osteoporosis.

Choices A and B: Multiple myeloma and metastatic disease should be included in the differential diagnosis when evaluating older adults with non-traumatic vertebral fractures. Findings in multiple myeloma include laboratory abnormalities, such as elevated serum calcium and creatinine levels, and constitutional symptoms such as weight loss.