USMLE PRACTICE QUESTION #60
TOPIC: MSK/Rheumatology
Today’s question will test your understanding of a commonly tested MSK topic.
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A 59-year-old female is visiting her primary care physician due to a persistent sense of fatigue and pain in her hands over the past three months. The patient reports experiencing more significant discomfort in the morning that diminishes gradually throughout the day. She denies any modification to her usual routine or any recent hand injuries. She has recently retired from her occupation as a paralegal. Clinical examination uncovers the presence of hyperextension in the proximal interphalangeal joints and flexion in the distal interphalangeal joints. Laboratory findings indicate elevated levels of ESR, CRP, and ferritin. Which of the following is responsible for these findings?
A. Supersaturation of uric acid in the extracellular fluid
B. Migration of CD4+ T cells to synovial joints
C. Decreased proteoglycans in the joint space
D. Sclerosis of subchondral bone
E. Deficiency of complement protein C2
Detailed Breakdown of Answers + Correct Answer Below ⏬
ANSWER + QUESTION BREAKDOWN
The mental model used to answer this question comes from our detailed test-taking skills masterclass. Here’s how to think through this question:
Step 1. Read the last line to determine what the question is asking: What’s responsible for her condition/symptoms?
Step 2: Is this a first-, second-, or third-order question?
Answer: 2nd order: 1st. Diagnose with the disorder. 2nd. Identify the underlying cause.
Step 3. Read the vignette to gather information.
Step 4. Consider the question and ask yourself the most likely answer.
Step 5. Look at the answer choices and select the option most closely resembling your thoughts from “Step 4” above.
GENERAL ANALYSIS
The clinical presentation suggests rheumatoid arthritis (RA), characterized by morning stiffness, pain in the hands, and specific joint deformities (hyperextension of proximal interphalangeal joints and flexion of distal interphalangeal joints). The laboratory findings of elevated ESR, CRP, and ferritin further support an inflammatory process. The task is to identify the mechanism responsible for joint inflammation and proliferation in this patient’s condition.
ANSWER CHOICES:
ANSWER CHOICE A: Supersaturation of uric acid in the extracellular fluid
Explanation: This mechanism is associated with gout, where uric acid crystals deposit in joints, causing inflammation.
ANSWER CHOICE B: Migration of CD4+ T cells to synovial joints
Explanation: In rheumatoid arthritis, CD4+ T cells migrate to synovial joints, leading to inflammation and proliferation of synovial tissue.
ANSWER CHOICE C: Decreased proteoglycans in the joint space
Explanation: Decreased proteoglycans are associated with osteoarthritis, where cartilage degradation occurs.
ANSWER CHOICE D: Sclerosis of subchondral bone
Explanation: Sclerosis of subchondral bone is a feature of osteoarthritis due to bone remodeling.
ANSWER CHOICE E: Deficiency of complement protein C2
Explanation: Complement deficiencies can lead to immune system dysfunction but are not directly related to RA pathogenesis.
FINAL VERDICT…
Rheumatoid arthritis is an autoimmune disease characterized by chronic inflammation of synovial joints. CD4+ T cells play a crucial role in the pathogenesis by migrating to the synovium, where they release cytokines that promote inflammation and proliferation of synovial tissue. This leads to joint damage and the characteristic symptoms observed in RA.
CORRECT ANSWER: B) Migration of CD4+ T cells to synovial joints
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