Myositis ossificans progressiva, unspecified ankle

This code signifies a rare, progressive genetic disorder characterized by the formation of bone in muscles, tendons, ligaments, and other connective tissues, specifically affecting an unspecified ankle. This heterotopic ossification leads to chronic pain, swelling, and progressive loss of joint mobility in the affected ankle.

Use this code when documentation clearly indicates a diagnosis of myositis ossificans progressiva with involvement of an unspecified ankle. This diagnosis is typically supported by clinical examination, imaging studies (e.g., X-rays, CT scans) showing heterotopic bone formation, and often genetic testing confirming the FOP diagnosis.

• Ensure documentation specifies "progressiva" to differentiate from localized myositis ossificans (M61.0-).
• Verify laterality if specified in the documentation; this code is for an unspecified ankle.
• Consider sequencing this code as a primary diagnosis when it is the main reason for the encounter.