Granulomatous reaction to collagen implant: light and electron microscopic observations.

A fifty-three-year-old woman noted bilateral linear confluent papules involving the nasolabial folds following injection of bovine collagen (Zyderm). On light microscopic examination the dermis contained epithelioid granulomas centered around the degenerated bovine collagen. Electron microscopic examination demonstrated the degraded collagen fibers, which could be easily differentiated from the native collagen. The patient's clinical findings, management, and the pathogenetic mechanisms of this entity are reviewed.