ICD-10 Code A51 – Early syphilis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A51 – Early syphilis
What it is
A51 identifies early syphilis, the initial stage of infection caused by Treponema pallidum. Use it when the record documents primary, secondary, or early latent syphilis.
Clinical signs
Clinical features vary; refer to documentation. Common findings include a painless chancre, rash, mucous patches, generalized lymphadenopathy, or early latent infection without symptoms.
When to use this code
Use A51 when the provider documents early syphilis without a more specific stage code. It also applies when the note clearly states primary, secondary, or early latent syphilis. Check documentation if the stage is unclear or if congenital or late disease is suspected.
Do not use for
Do not use A51 for late syphilis, neurosyphilis, or congenital syphilis. If the chart only says “syphilis” and does not specify stage, check documentation before coding.
Coding tip
Match the code to the documented stage, because syphilis codes are stage-specific and the record should support early disease.