Myositis ossificans progressiva, unspecified forearm

This code represents a rare, progressive genetic disorder characterized by the abnormal formation of bone in muscles, tendons, ligaments, and other connective tissues, specifically affecting an unspecified forearm. This heterotopic ossification leads to stiffness, pain, and significant functional impairment as the soft tissues gradually turn into bone.

Use this code when documentation confirms a diagnosis of myositis ossificans progressiva (fibrodysplasia ossificans progressiva) affecting an unspecified forearm. This diagnosis is typically made based on clinical presentation, genetic testing, and imaging studies showing heterotopic bone formation.

• Ensure the documentation clearly specifies "progressiva" to differentiate from myositis ossificans traumatica.
• Avoid using this code for localized, post-traumatic heterotopic ossification; those cases have distinct codes.
• If the specific forearm (right or left) is documented, use the more specific codes M61.131 or M61.132.