Myositis ossificans progressiva, unspecified lower leg

This code describes a rare, progressive genetic disorder characterized by the formation of bone in muscles, tendons, ligaments, and other connective tissues, specifically affecting an unspecified lower leg. This heterotopic ossification leads to significant functional impairment and restricted movement.

Use this code when documentation clearly indicates a diagnosis of myositis ossificans progressiva affecting an unspecified lower leg. This diagnosis is typically confirmed through clinical examination, imaging studies (e.g., X-rays, CT scans), and genetic testing. The "unspecified" nature implies that the laterality (left or right) of the affected lower leg is not documented.

• Ensure documentation specifies "progressiva" to differentiate from localized myositis ossificans.
• Avoid using this code if the laterality of the affected lower leg is known; instead, use the more specific codes M61.161 (right) or M61.162 (left).
• Code any associated functional limitations or complications, such as contractures or pain, with additional appropriate ICD-10-CM codes.