Myositis ossificans progressiva, left lower leg

This code describes a rare, severe genetic disorder characterized by progressive heterotopic ossification (bone formation in soft tissues) specifically affecting the left lower leg. This condition leads to debilitating stiffness and immobility as muscle, tendons, and ligaments gradually transform into bone.

Use this code when documentation confirms a diagnosis of myositis ossificans progressiva with the primary site of involvement being the left lower leg. This diagnosis is typically made based on clinical presentation, genetic testing (ACVR1 mutation), and imaging studies showing heterotopic bone formation.

• Ensure laterality is clearly documented (left lower leg) to support this specific code.
• Distinguish from myositis ossificans traumatica, which is localized and often follows injury (coded elsewhere).
• Consider sequencing this code as a primary diagnosis when it is the reason for the encounter, or as a secondary diagnosis when managing complications.