2026 ICD-10-CM Diagnosis Code A50.56Late congenital syphilitic osteochondropathy

ICD-10-CM Codes›A00–B99›A50-A64›A50

ICD-10-CM A50.56
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A50.56 is a billable ICD-10-CM diagnosis code for late congenital syphilitic osteochondropathy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 867 through 869. Coders also document this condition as arthritis caused by Spirochaetales. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified bone disease and musculoskeletal deformities, Perinatal infections, and Sexually transmitted infections (excluding HIV and hepatitis).

Code Identity

ICD-10-CM Code
A50.56
Billable Status
Yes — Valid for Submission
Code Describes
Late congenital syphilitic osteochondropathy
Short Description
Late congenital syphilitic osteochondropathy
Same as the full description in the CMS dataset.
Parent Code
A50.5
Other late congenital syphilis, symptomatic

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA50Congenital syphilis
This CodeA50.56Late congenital syphilitic osteochondropathy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Arthritis caused by Spirochaetales
  • Bowing deformity of lower leg
  • Late congenital syphilis
  • Late congenital syphilitic osteochondropathy
  • Saber shin
  • 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.

    • Anomaly, anomalous(congenital) (unspecified type)
      • tibia NEC
        • saber
    • Craniotabes(cause unknown)
      • syphilitic
    • Deformity
      • tibia (acquired)
        • saber (syphilitic)
    • Kyphosis, kyphotic(acquired)
      • syphilitic, congenital
    • Osteochondropathy
      • syphilitic, congenital
        • late
    • Saber, sabre shin or tibia(syphilitic)
    • Syphilis, syphilitic(acquired)
      • congenital
        • late, or 2 years or more after birth NEC
          • symptomatic or with manifestations NEC
            • osteochondropathy

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 PNL009
Perinatal infections
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF010
Sexually transmitted infections (excluding HIV and hepatitis)
Default principal diagnosis: inpatient No · outpatient No

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 A50.56 to ICD-9-CMHistory

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

ICD-9-CM
090.5 Late congen syph symptom
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 A50.56Overview

Is A50.56 (Other late congenital syphilis, symptomatic) a billable code?

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

What MS-DRG does A50.56 group to?

When late congenital syphilitic osteochondropathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 868, 869, with relative weights from 0.7297 to 2.0932 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A50.56?

Under the General Equivalence Mappings, late congenital syphilitic osteochondropathy converts to ICD-9-CM 090.5 (late congen syph symptom). 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.