FIBRODYSPLASIA OSSIFICANS CIRCUMSCRIPTA OF THE MASSETER MUSCLE

Fibrodysplasia ossificans circumscripta (FOC) is a lesion characterize d by localized calcification of the investing fascia of skeletal muscl e. It is often related to repeated trauma and was formerly known as tr aumatic myositis ossificans, Surgical procedures involving muscles are also believed to be a factor in the origin of the lesion. When FOC de velops in the muscles of mastication it can lead to severe trismus. A case is reported of FOC in the left masseter muscle of a 44-year-old m an who presented with marked limitation of opening. It was believed th at previous fractures of the left maxilla and mandible and/or the subs equent surgical treatments were responsible for the onset of FOC. The radiographic and microscopic features of FOC are discussed in relation to recent theories on the etiology, pathogenesis, and treatment of th e lesion.