A 65-year-old male develops the sudden onset of severe knee pain. The
knee is red, swollen, and tender. He has a history of diabetes mellitus
and cardiomyopathy. An x-ray of the knee shows linear calcification.
Definitive diagnosis is best made by
A. Serum uric acidb.
B. Serum calcium
C. Arthrocentesis and identification of positively birefringentrhomboid crystals
D. Rheumatoid factor
A. Serum uric acidb.
B. Serum calcium
C. Arthrocentesis and identification of positively birefringentrhomboid crystals
D. Rheumatoid factor
Ans. C. The acute mono-
articular arthritis in association with linear calcification of the cartilage
of the knee suggests the diagnosis of pseudogout, also called calcium
pyro-phosphate dihydrate deposition disease. The disease resembles gout.
Positive birefringent crystals (looking blue when parallel to the axis of the
red compensator on a polarizing microscope) can be demonstrated in joint fluid.
Serum uric acid and calcium levels are normal, as is the rheumatoid factor.
Pseudogout is about half as common as gout but becomes more common after age
65. Calcium pyrophosphate dihydrate deposition disease is diagnosed in
symptomatic patients by characteristic x-ray findings or crystals in synovial
fluid. The disease is treated with NSAIDs or colchicine. Linear calcifications
or chondrocalcinosis are often found in the joints of elderly patients who do
not have symptomatic joint problems; such patients do not require treatment.
