Fibrous dysplasia (monostotic), unspecified lower leg

This code signifies a benign bone disorder characterized by the replacement of normal bone with fibrous tissue in a single bone of the lower leg. This leads to weakened bone structure, which can result in pain, deformity, or fractures. It specifically refers to the monostotic form affecting an unspecified part of the lower leg.

Use this code when documentation confirms a diagnosis of fibrous dysplasia affecting only one bone in the lower leg, and the specific bone (e.g., tibia, fibula) is not identified. This diagnosis is typically made based on imaging studies (X-rays, MRI) and sometimes biopsy.

• Ensure documentation specifies "monostotic" and clearly indicates the lower leg as the affected area, without further anatomical specificity.
• Do not use this code if multiple bones are involved (polyostotic fibrous dysplasia) or if the specific bone in the lower leg is known.
• Consider additional codes for associated symptoms or complications, such as pathological fracture (M84.46-).