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ICD-10-CM 2027 diagnosis code

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

✓ Billable / specific

M85.021 is a valid, billable ICD-10-CM code for fibrous dysplasia (monostotic), right upper arm. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About M85.021

M85.021 is the ICD-10-CM diagnosis code for fibrous dysplasia (monostotic), right upper arm. 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 billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within M85.02 (fibrous dysplasia (monostotic), upper arm), M85.021 is specifically for fibrous dysplasia (monostotic), right upper arm. Related codes cover left upper arm (M85.022) and unspecified upper arm (M85.029).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 553 (Bone Diseases and Arthropathies with MCC, relative weight 1.2494) and DRG 554 (Bone Diseases and Arthropathies without MCC, relative weight 0.8331), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

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

Before ICD-10, this condition was coded in ICD-9-CM as 733.29 (other bone cyst).

Notes that apply from higher levels

Instructions written at a parent level also apply to M85.021.

› From M85.0 Fibrous dysplasia (monostotic)
Excludes2
  • fibrous dysplasia of jaw (M27.8)
› From M85 Other disorders of bone density and structure
Excludes1
  • osteogenesis imperfecta (Q78.0)
  • osteopetrosis (Q78.2)
  • osteopoikilosis (Q78.8)
  • polyostotic fibrous dysplasia (Q78.1)

Broader instructions also apply from Chapter 13: Diseases of the musculoskeletal system and connective tissue.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 08 · Diseases and Disorders of the Musculoskeletal System and Connective Tissue

ICD-9-CM equivalent

Converter →
  • 733.29Other bone cystapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about M85.021

Is M85.021 billable?

Yes. M85.021 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can M85.021 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict M85.021 as a principal diagnosis.

Is M85.021 a CC or MCC?

No. M85.021 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does M85.021 group to?

M85.021 is used in the MS-DRG v44.0 logic for MS-DRG 553 (Bone Diseases and Arthropathies with MCC) and MS-DRG 554 (Bone Diseases and Arthropathies without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for M85.021?

The CMS General Equivalence Mappings map M85.021 to ICD-9-CM 733.29.