2026 ICD-10-CM Diagnosis Code A50.55Late congenital syphilitic arthropathy

ICD-10-CM Codes›A00–B99›A50-A64›A50

ICD-10-CM A50.55
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A50.55 is a billable ICD-10-CM diagnosis code for late congenital syphilitic arthropathy. 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. 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
A50.55
Billable Status
Yes — Valid for Submission
Code Describes
Late congenital syphilitic arthropathy
Short Description
Late congenital syphilitic arthropathy
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 CodeA50.55Late congenital syphilitic arthropathy

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.

    • Arthritis, arthritic(acute) (chronic) (nonpyogenic) (subacute)
      • syphilitic (late)
        • congenital
    • Arthropathy
      • in (due to)
        • syphilis (late)
          • congenital
    • Hydrarthrosis
      • syphilitic (late)
        • congenital
    • Syphilis, syphilitic(acquired)
      • congenital
        • late, or 2 years or more after birth NEC
          • symptomatic or with manifestations NEC
            • arthropathy

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

Infectious Arthritis

Most kinds of arthritis cause pain and swelling in your joints. Joints are places where two bones meet, such as your elbow or knee. Infectious arthritis is an infection in the joint. The infection comes from a bacterial, viral, or fungal infection that spreads from another part of the body. Symptoms of infectious arthritis include:

Read the full article at MedlinePlus

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

Convert A50.55 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 A50.55Overview

Is A50.55 (Other late congenital syphilis, symptomatic) a billable code?

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

What MS-DRG does A50.55 group to?

When late congenital syphilitic arthropathy 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 A50.55?

Under the General Equivalence Mappings, late congenital syphilitic arthropathy 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.