2027 ICD-10-CM Diagnosis Code A51Early syphilis

ICD-10-CM Codes›A00–B99›A50-A64›A51

ICD-10-CM A51
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A51 is a non-billable ICD-10-CM category code for early syphilis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as A51.0, A51.1, A51.2, and A51.31.

Code Identity

ICD-10-CM Code
A51
Billable Status
No — Non-Billable Category
Code Describes
Early syphilis
Short Description
Early syphilis
Same as the full description in the CMS dataset.
Chapter
A50-A64
Infections with a predominantly sexual mode of transmission

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA51Early syphilis
This CodeA51Early syphilis

Specific Coding for Early syphilisOverview

Non-specific codes like A51 require more characters. Use one of these billable codes instead:

  • Use A51.0 for Primary genital syphilis

  • Use A51.1 for Primary anal syphilis

  • Use A51.2 for Primary syphilis of other sites

  • A51.3 for Secondary syphilis of skin and mucous membranes

  • Use A51.31 for Condyloma latum

  • Use A51.32 for Syphilitic alopecia

  • Use A51.39 for Other secondary syphilis of skin

  • A51.4 for Other secondary syphilis

  • Use A51.41 for Secondary syphilitic meningitis

  • Use A51.42 for Secondary syphilitic female pelvic disease

  • Use A51.43 for Secondary syphilitic oculopathy

  • Use A51.44 for Secondary syphilitic nephritis

  • Use A51.45 for Secondary syphilitic hepatitis

  • Use A51.46 for Secondary syphilitic osteopathy

  • Use A51.49 for Other secondary syphilitic conditions

  • Use A51.5 for Early syphilis, latent

  • Use A51.9 for Early syphilis, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A51: its own notes plus those printed at block A50-A64 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block A50-A64 Infections with a predominantly sexual mode of transmission applies to 142 codes
  • nonspecific and nongonococcal urethritis (N34.1)
  • Reiter's disease (M02.3-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block A50-A64 Infections with a predominantly sexual mode of transmission applies to 142 codes
  • human immunodeficiency virus [HIV] disease (B20)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A51, its category, or a range that includes it.

Applicable To 1

These notes mention A51.

  • O98.1 Syphilis complicating pregnancy, childbirth and the puerperium
    Conditions in A50-A53 names A50-A53, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming A51: its condition is not part of those codes, and both may be reported when the patient has both.

  • Block A65-A69 Other spirochetal diseases
    syphilis (A50-A53) names A50-A53, which includes this code

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.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A51Overview

What is the ICD-10 code for early syphilis?

A51 is the ICD-10-CM category for early syphilis, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is A51 (Early syphilis) a billable code?

No. This is a category header that groups the codes for early syphilis, and headers cannot be submitted on claims. Claims for early syphilis need a more specific code from this category, such as A51.0, A51.1, and A51.2.

Can A51 be reported with N34.1?

Not as a rule. The Excludes1 note at block A50-A64, which applies to A51, lists "nonspecific and nongonococcal urethritis (N34.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).