M85.0Fibrous dysplasia (monostotic)

M85.0 is the ICD-10-CM diagnosis code for fibrous dysplasia (monostotic). It belongs to category M85 (other disorders of bone density and structure), block M80-M85 (disorders of bone density and structure) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 10 subcodes must be used instead.

Within M85 (other disorders of bone density and structure), M85.0 is specifically for fibrous dysplasia (monostotic). Related codes cover skeletal fluorosis (M85.1), hyperostosis of skull (M85.2), Osteitis condensans (M85.3), Solitary bone cyst (M85.4), Aneurysmal bone cyst (M85.5), other cyst of bone (M85.6), other specified disorders of bone density and structure (M85.8) and disorder of bone density and structure, unspecified (M85.9).

To report this condition, pick the subcode that matches the documentation: M85.00 (unspecified site), M85.01 (shoulder), M85.02 (upper arm), M85.03 (forearm), M85.04 (hand), M85.05 (thigh), M85.06 (lower leg), M85.07 (ankle and foot) and 2 more.

The conditions in its Excludes2 note aren't part of M85.0, but may be coded alongside it if the patient has both: fibrous dysplasia of jaw (M27.8).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.