ICD-10 Code A51.0 – Primary genital syphilis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A51.0 – Primary genital syphilis
What it is
A51.0 identifies primary syphilis affecting the genital area. Use it when documentation shows an initial syphilitic lesion, usually a chancre, on the penis, vulva, vagina, cervix, or scrotum.
Clinical signs
Typical findings include a painless ulcer or erosion at the genital site and regional lymph node enlargement. Clinical features vary; refer to documentation.
When to use this code
Use A51.0 when the record clearly documents primary genital syphilis or a genital chancre due to syphilis. It fits the first recognized stage of infection before secondary or latent disease is documented. If the site or stage is unclear, check documentation before coding.
Do not use for
Do not use this code for secondary, latent, congenital, or unspecified syphilis. It is also not appropriate for non-syphilitic genital ulcers or lesions without documented syphilis.
Coding tip
Code the documented stage and site together; if either is missing, verify the note before assigning A51.0.