Myositis ossificans progressiva, unspecified thigh

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 thigh. The ossification leads to severe immobility and functional impairment.

Use this code when documentation confirms a diagnosis of myositis ossificans progressiva (also known as fibrodysplasia ossificans progressiva) with involvement of the thigh, but the laterality (right or left) is not specified. Supporting documentation would include genetic testing results, imaging studies showing heterotopic ossification, and clinical notes detailing progressive loss of range of motion.

• Ensure the documentation clearly states "progressiva" to differentiate from myositis ossificans traumatica.
• Avoid using this code if laterality of the affected thigh is specified; instead, select the more specific code (M61.151 or M61.152).
• Consider sequencing this code as a primary diagnosis if it is the main reason for the encounter, or as a secondary diagnosis if managing complications or related conditions.