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.
This month’s stumper
A 40-year-old woman has an eight-month history of diffuse joint pain and swelling that involves both hands and knees. She states that she cannot get any work done in the morning because of the pain, but it usually subsides as the day progresses.
She tires easily and constantly feels “feverish.” Her temperature is 37.8 °C (100 °F), blood pressure 110/70 mm Hg, pulse 60 beats per minute, and respirations 18 per minute. Physical examination shows tender, swollen and “boggy” hands and knees. Laboratory studies show hematocrit 34% and hemoglobin 10 g/dL.
A radiograph of this patient’s knee is most likely to show which of the following?
A. Bone erosions.
B. Osteophyte formation.
C. Subchondral cyst formation.
D. Subchondral sclerosis.
E. Subchondral tophi.
The correct answer is A.
Kaplan Medical explains why
This patient most likely has rheumatoid arthritis:
- Chronic inflammatory disorder characterized by symmetric joint involvement and extra-articular manifestations.
- Affects middle-aged women.
- Symptoms: joint pain and swelling, low-grade fever, malaise, fatigue, vasculitis, pericarditis, rheumatoid nodules, episcleritis and scleritis.
- Labs: normochromic, normocytic anemia, increased erythrocyte sedimentation rate and positive serum rheumatoid factor.
- Proximal interphalangeal joints (PIP), metacarpophalangeal joints (MCP), and the wrist joints are the most commonly involved joints. Distal interphalangeal joints (DIP) are usually spared.
- Radiographic findings: soft-tissue swelling, joint effusions, juxta-articular osteopenia, loss of articular cartilage, joint space narrowing and bone erosions.
- Treatment with disease modifying agents should be started within 3 months of diagnosis to reduce the risk of disease advancement. The treatment includes rest, physical therapy, NSAIDs, aspirin, corticosteroids, gold, methotrexate, penicillamine, cyclosporine, sulfasalazine and hydroxychloroquine.
Why the other answers are wrong
Choice B, C and D: Osteophyte formation, subchondral cyst formation and subchondral sclerosis are the radiographic findings of osteoarthritis. Osteoarthritis is a noninflammatory joint disease characterized by loss of articular cartilage and the aforementioned findings. The symptoms include a deep, aching joint pain that is aggravated by use and relieved by rest.
Physical examination shows joint tenderness, bony crepitus, warmth, and deformities (Heberden nodes and Bouchard nodes). Age, wear and tear, obesity, trauma and certain chronic conditions are factors that increase the risk for osteoarthritis. The treatment includes weight loss, physical therapy, acetaminophen and surgery.
Choice E: Subchondral tophi are found in gouty arthritis. They typically appear as “punched out” lesions of the subchondral bone. A tophus is a collection of urate crystals, inflammatory cells, and fibrosis. Tophi can lead to cartilage and bone destruction.
Tips to remember
- Rheumatoid arthritis (RA) is an autoimmune disease with symmetrical joint involvement occurring in young adults.
- RA is usually accompanied by constitutional findings and other autoimmune symptoms, whereas osteoarthritis is not.
- Bony erosions seen on radiograph are characteristic.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
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