2026 ICD-10-CM Diagnosis Code A66.6Bone and joint lesions of yaws

ICD-10-CM Codes›A00–B99›A65-A69›A66

ICD-10-CM A66.6
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A66.6 is a billable ICD-10-CM diagnosis code for bone and joint lesions of yaws. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 548 through 550. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Parasitic, other specified and unspecified infections.

For Medicare Advantage risk adjustment, A66.6 maps to CMS-HCC Category 92 (Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis) under the V28 model, adding a risk factor of about 0.479 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
A66.6
Billable Status
Yes — Valid for Submission
Code Describes
Bone and joint lesions of yaws
Short Description
Bone and joint lesions of yaws
Same as the full description in the CMS dataset.
Parent Code
A66
Yaws

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA65-A69Other spirochetal diseases
CategoryA66Yaws
This CodeA66.6Bone and joint lesions of yaws

Medicare Risk Adjustment (HCC)Billing

A66.6 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.

CMS-HCC V28 Category (Payment Model)
HCC 92— Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
Payment HCC · PY 2026 one of 609 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.479
community, non-dual, aged · ranges 0.471–0.632 across segments
Hierarchy
Top of its hierarchy
HCC 92 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 39
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 39 · ESRD (V21): HCC 39 · ESRD (V24): HCC 39
ESRD V21 weights: 0.061 dialysis, 0.375–0.468 functioning graft · ESRD V24 weights: 0.092 dialysis, 0.431–0.578 functioning graft
Part D (RxHCC)
Not mapped
A66.6 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Arthritis caused by Spirochaetales
  • Bone and/or joint yaws lesions
  • Exostosis of jaw
  • Exostosis of skull
  • Ganglion of yaws
  • Goundou of yaws
  • Gummatous osteitis of yaws
  • Gummatous periostitis of yaws
  • Hydrarthrosis of yaws
  • Hypertrophic periostitis of yaws
  • Yaws gumma of bone
  • Yaws of joint
  • Yaws osteitis
  • Yaws periostitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Yaws ganglion
  • Yaws goundou
  • Yaws gumma, bone
  • Yaws gummatous osteitis or periostitis
  • Yaws hydrarthrosis
  • Yaws osteitis
  • Yaws periostitis (hypertrophic)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF009
Parasitic, other specified and unspecified infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Yaws

    a systemic non-venereal infection of the tropics caused by treponema pallidum subspecies pertenue.

  • Treponema pallidum

    the causative agent of venereal and non-venereal syphilis as well as yaws.

  • Early Yaws

    early yaws includes primary and secondary stages of yaws, endemic tropical treponemal nonvenereal infection: development of initial lesion at inoculation site followed by widespread dissemination of treponemes and generalized secondary granulomatous lesions that may relapse repeatedly.

  • Late Yaws

    late yaws is the tertiary, non-contagious stage of yaws, endemic tropical treponemal nonvenereal infection. late yaws is characterized by destructive and deforming lesions of the skin, bones, and joints.

  • Yaws

    an endemic, infectious, nonvenereal disease in humans that presents mainly in children younger than 15 years. the disease occurs primarily in warm, humid, tropical areas of africa, asia, south america, and oceania, among poor rural populations where conditions of overcrowding and poor sanitation prevail. infection with treponema pertenue, a subspecies of treponema pallidum, causes the disease.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A66.6 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
102.6 Yaws of bone & joint
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A66.6Overview

What is the ICD-10 code for bone and joint lesions of yaws?

The ICD-10-CM code for bone and joint lesions of yaws is A66.6 (sometimes written as A666). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A66.6 (Yaws) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report bone and joint lesions of yaws on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A66.6 group to?

When bone and joint lesions of yaws is the principal diagnosis on an inpatient stay, it groups to MS-DRG 548, 549, 550, with relative weights from 0.8741 to 1.9309 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A66.6?

Under the General Equivalence Mappings, bone and joint lesions of yaws converts to ICD-9-CM 102.6 (yaws of bone & joint). The mapping is a direct match.

What HCC is A66.6?

A66.6 (bone and joint lesions of yaws) maps to CMS-HCC Category 92 (Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis), commonly written as HCC 92, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 39 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.

Does A66.6 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, A66.6 adds a risk adjustment factor of about 0.479 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.471 to 0.632 depending on the payment segment). HCC 92 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 92 category page.