Multifactorial refractory heterotopic ossification.

Ectopic bone formation or "heterotopic ossification" can follow surgery, trauma, or neurologic injury, but the process is usually self-limited, localized to the site of injury, and responds to surgical treatment when necessary. Aggressive, systemic forms of heterotopic ossification exist that generate lesions that often resist surgical treatment and produce a high rate of recurrence. These entities typically manifest during infancy as genetic syndromes such as fibrodysplasia ossificans progressiva or progressive osseous heteroplasia.