Myositis ossificans progressiva, unspecified site

This code represents fibrodysplasia ossificans progressiva (FOP), a rare, severe genetic disorder characterized by progressive heterotopic ossification (bone formation in soft tissues). It leads to the gradual replacement of muscles, tendons, and ligaments with bone, causing severe immobility and skeletal deformities. The "unspecified site" indicates that the specific anatomical location of the ossification is not documented.

Use this code when documentation confirms a diagnosis of fibrodysplasia ossificans progressiva, and the medical record does not specify the particular body region affected by the heterotopic ossification. This code is appropriate for initial diagnoses or follow-up encounters where the site is not a primary focus of the visit or remains generalized.

• Avoid using this code if a specific site of ossification (e.g., shoulder, hip) is documented; instead, use a more specific M61.1- subcategory.
• Always review the entire medical record for any mention of specific anatomical involvement before defaulting to the "unspecified site" code.
• Consider sequencing this code as a primary diagnosis when FOP is the chief reason for the encounter, or as a secondary diagnosis when managing complications related to the condition.