M85.021 Fibrous dysplasia (monostotic), right upper arm

Billable ICD-10-CM code, FY2026.

Applies from M85 Other disorders of bone density and structure

Excludes1 (never code together)

• osteogenesis imperfecta (Q78.0)
• osteopetrosis (Q78.2)
• osteopoikilosis (Q78.8)
• polyostotic fibrous dysplasia (Q78.1)

Applies from M85.0 Fibrous dysplasia (monostotic)

Excludes2 (not included here)

• fibrous dysplasia of jaw (M27.8)

MS-DRG index

Defines the logic of DRG(s) 553-554 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 733.29 Other bone cyst (approximate)

Nearby codes

• M85.01 Fibrous dysplasia (monostotic), shoulder
• M85.011 Fibrous dysplasia (monostotic), right shoulder
• M85.012 Fibrous dysplasia (monostotic), left shoulder
• M85.019 Fibrous dysplasia (monostotic), unspecified shoulder
• M85.02 Fibrous dysplasia (monostotic), upper arm
• M85.021 Fibrous dysplasia (monostotic), right upper arm (this code)
• M85.022 Fibrous dysplasia (monostotic), left upper arm
• M85.029 Fibrous dysplasia (monostotic), unspecified upper arm
• M85.03 Fibrous dysplasia (monostotic), forearm
• M85.031 Fibrous dysplasia (monostotic), right forearm
• M85.032 Fibrous dysplasia (monostotic), left forearm