A51 – Early syphilis
ICD-10-CM 2027 diagnosis code · Infections with a predominantly sexual mode of transmission
ICD-10-CM code
A51
- Code
A51(claims format:A51)- Description
- Early syphilis
- Billable
- No – use a more specific code below
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 1. Certain infectious and parasitic diseases (A00-B99)
- Block
- A50-A64 Infections with a predominantly sexual mode of transmission
Billable codes under A51
A51 is a header code and cannot be used on claims. Choose the most specific code:
- A51.0 – Primary genital syphilisBillable
- A51.1 – Primary anal syphilisBillable
- A51.2 – Primary syphilis of other sitesBillable
- A51.3 – Secondary syphilis of skin and mucous membranesHeader (more codes below)
- A51.4 – Other secondary syphilisHeader (more codes below)
- A51.5 – Early syphilis, latentBillable
- A51.9 – Early syphilis, unspecifiedBillable
Notes inherited from parent codes
Instructional notes at a category or block level apply to every code below it.
Block A50-A64
Excludes1 (not coded here):
Excludes2 (not included here):
- human immunodeficiency virus [HIV] disease (B20)
Frequently asked questions
What is ICD-10 code A51?
A51 is the ICD-10-CM code for early syphilis, in the block A50-A64 (Infections with a predominantly sexual mode of transmission).
Is A51 a billable code?
No. A51 is a header code with more specific child codes; report one of the billable codes listed above.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.