2026 ICD-10-CM Diagnosis Code A51.46Secondary syphilitic osteopathy

ICD-10-CM Codes›A00–B99›A50-A64›A51

ICD-10-CM A51.46
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A51.46 is a billable ICD-10-CM diagnosis code for secondary syphilitic osteopathy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 539 through 541. Coders also document this condition as secondary syphilis of bone. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified bone disease and musculoskeletal deformities and Sexually transmitted infections (excluding HIV and hepatitis).

Code Identity

ICD-10-CM Code
A51.46
Billable Status
Yes — Valid for Submission
Code Describes
Secondary syphilitic osteopathy
Short Description
Secondary syphilitic osteopathy
Same as the full description in the CMS dataset.
Parent Code
A51.4
Other secondary syphilis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA51Early syphilis
This CodeA51.46Secondary syphilitic osteopathy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Secondary syphilis of bone
  • Secondary syphilis of musculoskeletal system
  • Secondary syphilitic periostitis
  • Syphilis of bone

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Periostitis(albuminosa) (circumscribed) (diffuse) (infective) (monomelic)
      • syphilitic
        • secondary
    • Syphilis, syphilitic(acquired)
      • bone
        • secondary
    • Syphilis, syphilitic(acquired)
      • periosteum (late)
        • early (secondary)
    • Syphilis, syphilitic(acquired)
      • secondary (and primary)
        • bone
    • Syphilis, syphilitic(acquired)
      • secondary (and primary)
        • periosteum, periostitis

Clinical ClassificationClinical

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

CCSR MUS028
Other specified bone disease and musculoskeletal deformities
Default principal diagnosis: inpatient No · outpatient No
CCSR INF010
Sexually transmitted infections (excluding HIV and hepatitis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Secondary Syphilis

    the secondary stage of syphilis typically that is characterized by generalized rash (including palms and soles), mucocutaneous lesions, and lymphadenopathy. it usually begins one to two months after the primary stage.

Patient EducationClinical

Bone Infections

Like other parts of the body, bones can get infected. The infections are usually bacterial, but can also be fungal. They may spread to the bone from nearby skin or muscles, or from another part of the body through the bloodstream.

Read the full article at MedlinePlus

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

Convert A51.46 to ICD-9-CMHistory

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

ICD-9-CM
091.61 Syphilitic periostitis
Approximate The match is approximate rather than exact.

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 A51.46Overview

Is A51.46 (Other secondary syphilis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report secondary syphilitic osteopathy on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A51.46 group to?

When secondary syphilitic osteopathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 539, 540, 541, with relative weights from 0.7715 to 1.9697 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A51.46?

Under the General Equivalence Mappings, secondary syphilitic osteopathy converts to ICD-9-CM 091.61 (syphilitic periostitis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.