A51.0 Primary genital syphilis

The ICD-10-CM code for Primary genital syphilis is A51.0 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

1: Certain infectious and parasitic diseases (A00-B99)

Section

A50-A64: Infections with a predominantly sexual mode of transmission (A50-A64)

Category A51

18 codes (15 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to A51.0:

• Chancre (any genital site) (hard) (hunterian) (mixed) (primary) (seronegative) (seropositive) (syphilitic)
• Syphilis, syphilitic (acquired) › penis (chancre)
• Bubo › syphilitic (primary)
• Syphilis, syphilitic (acquired) › bubo (primary)
• Chancre (any genital site) (hard) (hunterian) (mixed) (primary) (seronegative) (seropositive) (syphilitic) › urethra
• Lesion (s) (nontraumatic) › primary
• Syphilis, syphilitic (acquired) › chancre (multiple)
• Syphilis, syphilitic (acquired) › genital (primary)

Inclusion Terms

• Syphilitic chancre NOS

U.S. Hospital Utilization

• An estimated 565 U.S. inpatient stays in 2023 included A51.0 among the documented diagnoses.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

HIV Infections (TOC entry)

a. Human Immunodeficiency Virus (HIV) Infections .............................................................. 19

Infectious agents causing diseases in other chapters (TOC)

b. Infectious agents as the cause of diseases classified to other chapters ................................. 22

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)