A 54-year-old woman comes to the physician because of constant dull pain, swelling, and progressive stiffness of the right knee for 3 days. Use of over-the-counter analgesics has only provided minimal relief of her symptoms. She has not had any similar symptoms in the past. She takes hydrochlorothiazide for hypertension. Examination of the right knee shows a large effusion and mild erythema. There is moderate tenderness to palpation. Range of motion is limited by pain. Arthrocentesis of the right knee is performed, and microscopic examination of the synovial fluid under polarized light is shown. These crystals are most likely composed of which of the following substances?

Question

A 54-year-old woman comes to the physician because of constant dull pain, swelling, and progressive stiffness of the right knee for 3 days. Use of over-the-counter analgesics has only provided minimal relief of her symptoms. She has not had any similar symptoms in the past. She takes hydrochlorothiazide for hypertension. Examination of the right knee shows a large effusion and mild erythema. There is moderate tenderness to palpation. Range of motion is limited by pain. Arthrocentesis of the right knee is performed, and microscopic examination of the synovial fluid under polarized light is shown.  These crystals are most likely composed of which of the following substances?

Quizplus · Accepted Answer

Eductional Objective: Synovial fluid analysis showing rhomboid-shaped calcium pyrophosphate dihydrate crystals is diagnostic of pseudogout.  These crystals are positively birefringent under compensated polarized light.  The knee joint is involved in >50% of cases.

A 54-Year-Old Woman Comes to the Physician Because of Constant