Wednesday, October 10, 2018

Repeated USMLE Questions Step 1- 233

A 56- year old man presents to the clinic due to recurrent attacks of severe pain in his right big toe for the last few weeks. During the attacks, his toe becomes painful, red, warm and swollen. Significant improvement occurs after treatment with colchicine. Synovial fluid analysis is performed to confirm the diagnosis.

What is the most likely finding to confirm the diagnosis?

A- Calcium oxalate crystals

B- Calcium pyrophosphate dehydrate crystals

C- Cholesterol crystals

D- Cloudy, reddish fluid, with leucocytes’ count equal to the blood count

E- Negatively birefringent urate crystals


This is a case of gout supported by the patient complaint of recurrent inflammation of the big toe and improvement of symptoms after the use of colchicine. Acute gout is confirmed by the detection of negatively birefringent monosodium urate crystals in synovial fluid analysis. Calcium pyrophosphate dehydrate crystals are found in cases of pseudo-gout. Acute arthritis is characterized by cloudy, bloody synovial fluid with leucocytes count equal to the blood count (normally synovial fluid may contain up to 200 cells /UL white blood cells). Cholesterol crystals are seen in patients with hypercholesterolemia and rheumatoid arthritis while calcium oxalate crystals can be seen in patient with renal diseases on dialysis.

The correct answer is E

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