M85.042 ICD-10-CM Code: Fibrous dysplasia (monostotic), left hand
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Disorders of bone density and structure (M80-M85)
M85.042
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceFibrous dysplasia (monostotic), left hand
A benign bone condition where fibrous tissue abnormally grows in the left hand bone, causing the bone structure to weaken and potentially affect hand function.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M85.042 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M85.042 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M85.042 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M85.042 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M85.042 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M85.042 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M85.042 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M85.042 an HCC code?
No. M85.042 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
- Code
- M85.042
- Description
- Fibrous dysplasia (monostotic), left hand
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
Get the V28 RAF + MEAT cheat sheet
One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.
Free PDF. No card. Unsubscribe anytime.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
M85.042 is the ICD-10-CM diagnosis code for fibrous dysplasia (monostotic), left hand. A benign bone condition where fibrous tissue abnormally grows in the left hand bone, causing the bone structure to weaken and potentially affect hand function. M85.042 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering disorders of bone density and structure (m80-m85).
M85.042 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Verify laterality is documented as 'left' in the medical record before assigning this code.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M85.042 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify laterality is documented as 'left' in the medical record before assigning this code
- •This code applies to any bone in the left hand, including metacarpals and phalanges