2026 ICD-10-CM Diagnosis Code A51.5Early syphilis, latent

ICD-10-CM Codes›A00–B99›A50-A64›A51

ICD-10-CM A51.5
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A51.5 is a billable ICD-10-CM diagnosis code for early syphilis, latent. 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 Sexually transmitted infections (excluding HIV and hepatitis).

Code Identity

ICD-10-CM Code
A51.5
Billable Status
Yes — Valid for Submission
Code Describes
Early syphilis, latent
Short Description
Early syphilis, latent
Same as the full description in the CMS dataset.
Parent Code
A51
Early syphilis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA51Early syphilis
This CodeA51.5Early syphilis, latent

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired syphilis
  • Acquired syphilis - early latent
  • Early latent syphilis, positive serology, negative cerebrospinal fluid, less than 2 years after infection
  • Early latent syphilis, positive serology, negative cerebrospinal fluid, with relapse after treatment
  • Latent early syphilis
  • Latent syphilis
  • Latent syphilis with positive serology
  • Serological relapse after treatment of latent early syphilis

Tabular List NotesGuidance

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

Inclusion Terms

  • Syphilis (acquired) without clinical manifestations, with positive serological reaction and negative spinal fluid test, less than two years after infection.

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.

    • Syphilis, syphilitic(acquired)
      • early
        • latent (without manifestations) (less than 2 years after infection)
    • Syphilis, syphilitic(acquired)
      • early
        • latent (without manifestations) (less than 2 years after infection)
          • negative spinal fluid test
    • Syphilis, syphilitic(acquired)
      • early
        • latent (without manifestations) (less than 2 years after infection)
          • serological relapse after treatment
    • Syphilis, syphilitic(acquired)
      • early
        • latent (without manifestations) (less than 2 years after infection)
          • serology positive
    • Syphilis, syphilitic(acquired)
      • latent
        • early, or less than 2 years after infection
    • Syphilis, syphilitic(acquired)
      • latent
        • positive serology (only finding)
          • early, or less than 2 years after infection

Clinical ClassificationClinical

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

CCSR INF010
Sexually transmitted infections (excluding HIV and hepatitis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Early Latent Syphilis

    latent syphilis when infection was acquired less than twelve months previously.

  • Late Latent Syphilis

    latent syphilis when infection was acquired more than twelve months previously.

  • Latent Syphilis

    a stage of syphilis characterized by the serologic evidence of infection by treponema pallidum without evidence of accompanying signs or symptoms related to the disease.

Patient EducationClinical

Syphilis

Syphilis is a sexually transmitted infection (STI) caused by bacteria. It infects the genital area, lips, mouth, or anus of both men and women. You usually get syphilis from sexual contact with someone who has it. It can also pass from mother to baby during pregnancy.

Read the full article at MedlinePlus

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

Convert A51.5 to ICD-9-CMHistory

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

ICD-9-CM
092.0 Early syph latent relaps
Approximate The match is approximate rather than exact.
ICD-9-CM
092.9 Early syphil latent NOS
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 A51.5Overview

Is A51.5 (Early syphilis) a billable code?

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

What MS-DRG does A51.5 group to?

When early syphilis, latent 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 A51.5?

Under the General Equivalence Mappings, early syphilis, latent converts to ICD-9-CM 092.0 (early syph latent relaps) and 092.9 (early syphil latent NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.