If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 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.  

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Your patient is extremely distressed at a worsening tightening of the skin developing around the face and hands. The patient also has epigastric pain radiating into the chest. There is no shortness of breath or hypertension. Chest x-ray is normal and BUN and creatinine are normal. Echocardiography shows a pulmonary artery pressure that is elevated. Pulmonary function testing is planned. The patient asks about her prognosis.

Which of the following represents the greatest difference between limited scleroderma (CREST syndrome) and diffuse systemic sclerosis?

A.  Anti-centromere antibodies.


C. Raynaud's phenomenon.

D. Esophageal dysmotility.

E. Hand involvement.

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The correct answer is A.

Anti-centromere antibodies are present in almost all patients with CREST syndrome (90%) but in virtually no patients (less than 5%) with diffuse systemic sclerosis (scleroderma).

Choice B: The ANA is present in the majority of patients with both syndromes.

Choice C, D and E: Raynaud's phenomenon, esophageal dysmotility, and hand involvement known as sclerodactyly are present in both syndromes. Esophageal dysmotility manifests as gastroesophageal reflux disease in both patient groups.

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Anti-centromere antibodies are present in CREST syndrome, but not in diffuse systemic sclerosis (scleroderma).

For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.

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