ICD-10-CM 2027
ICD-10 code for early syphilis
From the official ICD-10-CM alphabetic index entry “Syphilis, syphilitic (acquired) › early”. Page updated September 29, 2026.
About coding early syphilis
The ICD-10-CM code for early syphilis is A51.9 (Early syphilis, unspecified). The official index lists 14 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on A51.9.
Within A51, choose A51.9 (unspecified) only when documentation doesn't support a more specific option: primary genital syphilis (A51.0), primary anal syphilis (A51.1), primary syphilis of other sites (A51.2), secondary syphilis of skin and mucous membranes (A51.3), other secondary syphilis (A51.4) and latent (A51.5).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235) and DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific early syphilis codes (official index)
- cardiovascular A52.00 — Cardiovascular syphilis, unspecified
- central nervous system A52.3 — Neurosyphilis, unspecified
- latent (without manifestations) (less than 2 years after infection) A51.5 — Early syphilis, latent
- negative spinal fluid test A51.5 — Early syphilis, latent
- serological relapse after treatment A51.5 — Early syphilis, latent
- serology positive A51.5 — Early syphilis, latent
- relapse (treated, untreated) A51.9 — Early syphilis, unspecified
- skin A51.39 — Other secondary syphilis of skin
- symptomatic A51.9 — Early syphilis, unspecified
- extragenital chancre A51.2 — Primary syphilis of other sites
- primary, except extragenital chancre A51.0 — Primary genital syphilis
- secondary A51.39 — Other secondary syphilis of skin
- relapse (treated, untreated) A51.49 — Other secondary syphilitic conditions
- ulcer A51.39 — Other secondary syphilis of skin
Common questions about early syphilis ICD-10 codes
What is the ICD-10 code for early syphilis?
- A51.9 — Early syphilis, unspecified. More specific codes apply when the documentation supports them: A52.00, A52.3, A51.5, A51.5 and others below.
What is the ICD-10 code for cardiovascular early syphilis?
- A52.00 — Cardiovascular syphilis, unspecified.
What is the ICD-10 code for central nervous system early syphilis?
- A52.3 — Neurosyphilis, unspecified.
What is the ICD-10 code for latent early syphilis?
- A51.5 — Early syphilis, latent.
What is the ICD-10 code for relapse early syphilis?
- A51.9 — Early syphilis, unspecified.
What is the ICD-10 code for skin early syphilis?
- A51.39 — Other secondary syphilis of skin.
What is the ICD-10 code for symptomatic early syphilis?
- A51.9 — Early syphilis, unspecified.
Is A51.9 billable?
- Yes. A51.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A51.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A51.9 as a principal diagnosis.
Is A51.9 a CC or MCC?
- No. A51.9 is neither a CC nor an MCC under MS-DRG v44.0.