Pseudogout associated with the use of cyclical etidronate therapy.

Recently the use of etidronate in a cyclical fashion has been shown to be of value in the treatment of osteoporosis. Like all bisphosphonates etidronate is structurally similar to pyrophosphate, further it is also known to interfere with phosphate handling by the kidney resulting in elevated plasma phosphate levels. This report describes the case of a patient with established osteoporosis who developed pseudogout associated with cyclical etidronate use. The possible mechanism responsible for this is discussed.