ICD-10-CM 2027 diagnosis code

A51Early syphilis

Not billable — use a more specific code

A51 is a header code, so it can't be reported by itself. Choose one of the 7 more specific codes beneath it.

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

A51 is the ICD-10-CM diagnosis code for early syphilis. It belongs to block A50-A64 (infections with a predominantly sexual mode of transmission) and chapter 1 (certain infectious and parasitic diseases). It is a header code, so it can't be reported by itself; one of its 7 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: A51.0 (syphilis), A51.1 (syphilis), A51.2 (sites), A51.3 (membranes), A51.4 (syphilis), A51.5 (latent) and A51.9 (unspecified).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under A51

Notes that apply from higher levels

Instructions written at a parent level also apply to A51.

Broader instructions also apply from A50-A64 Infections with a predominantly sexual mode of transmission and Chapter 1: Certain infectious and parasitic diseases.

Code history

2016
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2021
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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

Is A51 billable?: No. A51 is a header code. Report one of its more specific subcodes instead.