Myositis ossificans progressiva, other site

This code describes a rare, progressive genetic disorder characterized by the formation of bone in muscles, tendons, ligaments, and other connective tissues, specifically when occurring in anatomical sites other than the head, neck, shoulder, upper arm, forearm, hand, thigh, lower leg, or ankle/foot. This heterotopic ossification leads to significant functional impairment and joint immobility over time.

Use this code for documented cases of myositis ossificans progressiva affecting locations not specified by more granular codes (e.g., trunk, pelvis, multiple sites not individually specified). Documentation should clearly indicate the diagnosis of fibrodysplasia ossificans progressiva (FOP) and specify the affected "other" anatomical site(s) where heterotopic ossification is occurring.

• Ensure the documentation explicitly states "myositis ossificans progressiva" or "fibrodysplasia ossificans progressiva" to differentiate from localized myositis ossificans.
• Verify that the affected site is not covered by more specific codes within the M61.1 subcategory (e.g., M61.11-M61.17).
• Code additional manifestations or complications of FOP, such as contractures or pain, with appropriate secondary codes.