Pseudogout

Pseudogout is a form of microcrystal synovitis caused by the deposition of calcium pyrophosphate dihydrate in the synovium

Risk factors

• hyperparathyroidism
• hypothyroidism
• haemochromatosis
• acromegaly
• low magnesium, low phosphate
• Wilson's disease

Features

• knee, wrist and shoulders most commonly affected
• joint aspiration: weakly-positively birefringent rhomboid shaped crystals
• x-ray: chondrocalcinosis

Management

• aspiration of joint fluid, to exclude septic arthritis
• NSAIDs or intra-articular, intra-muscular or oral steroids as for gout