ICD-10-CM 2027 diagnosis code
A51.0Primary genital syphilis
A51.0 is a valid, billable ICD-10-CM code for primary genital syphilis. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for Chancre, ICD-10 code for Primary lesion, ICD-10 code for Vulva syphilis, ICD-10 code for Primary syphilis.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About A51.0
A51.0 is the ICD-10-CM diagnosis code for primary genital syphilis. It belongs to category A51 (early syphilis), block A50-A64 (infections with a predominantly sexual mode of transmission) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within A51 (early syphilis), A51.0 is specifically for primary genital syphilis. Related codes cover primary anal syphilis (A51.1), primary syphilis of other sites (A51.2), secondary syphilis of skin and mucous membranes (A51.3), other secondary syphilis (A51.4), latent (A51.5) and unspecified (A51.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 727 (Inflammation of the Male Reproductive System with MCC, relative weight 1.37), DRG 728 (Inflammation of the Male Reproductive System without MCC, relative weight 0.8224), DRG 742 (Uterine and Adnexa Procedures for Non-Malignancy with CC/MCC, relative weight 1.8456), DRG 743 (Uterine and Adnexa Procedures for Non-Malignancy without CC/MCC, relative weight 1.2974), DRG 757 (Infections, Female Reproductive System with MCC, relative weight 1.4649), DRG 758 (Infections, Female Reproductive System with CC, relative weight 0.9908) and 1 more, in MDC 12 (Diseases and Disorders of the Male Reproductive System) and MDC 13 (Diseases and Disorders of the Female Reproductive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 091.0 (genital syphilis (primary)).
Coding notes
- Syphilitic chancre NOS
Notes that apply from higher levels
Instructions written at a parent level also apply to A51.0.
Broader instructions also apply from A50-A64 Infections with a predominantly sexual mode of transmission and Chapter 1: Certain infectious and parasitic diseases.
Alphabetic index entries
17 entriesTerms in the official ICD-10-CM index that lead to A51.0.
- Bubo › syphilitic (primary)
- Chancre (any genital site) (hard) (hunterian) (mixed) (primary) (seronegative) (seropositive) (syphilitic)
- Chancre (any genital site) (hard) (hunterian) (mixed) (primary) (seronegative) (seropositive) (syphilitic) › urethra
- Lesion (s) (nontraumatic) › primary
- Syphilis, syphilitic (acquired) › bubo (primary)
- Syphilis, syphilitic (acquired) › chancre (multiple)
- Syphilis, syphilitic (acquired) › chancre (multiple) › Rollet's
- Syphilis, syphilitic (acquired) › early › symptomatic › primary, except extragenital chancre
- Syphilis, syphilitic (acquired) › genital (primary)
- Syphilis, syphilitic (acquired) › penis (chancre)
- Syphilis, syphilitic (acquired) › primary
- Syphilis, syphilitic (acquired) › primary › genital
- Syphilis, syphilitic (acquired) › vagina
- Syphilis, syphilitic (acquired) › vulva
- Ulcus › durum (syphilitic)
- Vaginitis (acute) (circumscribed) (diffuse) (emphysematous) (nonvenereal) (ulcerative) › syphilitic (early)
- Vulvitis (acute) (allergic) (atrophic) (hypertrophic) (intertriginous) (senile) › syphilitic (early)
Codes whose notes reference A51.0
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 12 · Diseases and Disorders of the Male Reproductive System
MDC 13 · Diseases and Disorders of the Female Reproductive System
MDC 13 · Diseases and Disorders of the Female Reproductive System
ICD-9-CM equivalent
Converter →- 091.0Genital syphilis (primary)exact
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about A51.0
Is A51.0 billable?
- Yes. A51.0 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A51.0 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A51.0 as a principal diagnosis.
Is A51.0 a CC or MCC?
- No. A51.0 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does A51.0 group to?
- A51.0 is used in the MS-DRG v44.0 logic for MS-DRG 727 (Inflammation of the Male Reproductive System with MCC), MS-DRG 728 (Inflammation of the Male Reproductive System without MCC), MS-DRG 742 (Uterine and Adnexa Procedures for Non-Malignancy with CC/MCC), MS-DRG 743 (Uterine and Adnexa Procedures for Non-Malignancy without CC/MCC), MS-DRG 757 (Infections, Female Reproductive System with MCC), MS-DRG 758 (Infections, Female Reproductive System with CC) and 1 more. Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for A51.0?
- The CMS General Equivalence Mappings map A51.0 to ICD-9-CM 091.0.