A51.1 Primary anal syphilis

Billable ICD-10-CM code, FY2026.

MS-DRG index

Defines the logic of DRG(s) 393-395 in MDC 06.

Approximate ICD-9-CM (GEMs)

• 091.1 Primary anal syphilis

Code annotations containing back-references to A51.1

Back-references to A51

• Type 2 Excludes: N34 Urethritis and urethral syndrome ("urethritis in diseases with a predominantly sexual mode of transmission (A50-A64)")

Diagnosis Index entries for A51.1

• Induration, indurated › chancre › anus
• Syphilis, syphilitic (acquired) › anus (late) › primary
• Syphilis, syphilitic (acquired) › primary › anal

Nearby codes

• A51 Early syphilis
• A51.0 Primary genital syphilis
• A51.1 Primary anal syphilis (this code)
• A51.2 Primary syphilis of other sites
• A51.3 Secondary syphilis of skin and mucous membranes
• A51.31 Condyloma latum
• A51.32 Syphilitic alopecia
• A51.39 Other secondary syphilis of skin