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A53.9 ICD-10-CM Code: Syphilis, unspecified

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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Infections with a predominantly sexual mode of transmission (A50-A64)

A53.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Syphilis, unspecified

This code is used when a patient has syphilis (a sexually transmitted bacterial infection) but the specific stage or type has not been determined or documented. Syphilis can affect multiple body systems and requires treatment with antibiotics.

CMS-HCC V28

N/A

—

Not mapped

CMS-HCC V24

N/A

—

Not mapped

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

N/A

—

Not mapped

RXHCC

N/A

—

Not mapped

Code Book Path

Official
A53Other and unspecified syphilis
A53.9Syphilis, unspecified

Inclusion Terms

Official
  • Infection due to Treponema pallidum NOS
  • Syphilis (acquired) NOS

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A53.9 in this effective period.

Related Child Codes

Official
A53.0Latent syphilis, unspecified as early or late

Includes

Official

ICD-10-CM does not list Includes notes for A53.9 in this effective period.

Excludes 1

Official
  • syphilis NOS under two years of age (A50.2)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for A53.9 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A53.9 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A53.9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Use this code only when the documentation does not specify the stage of syphilis (primary, secondary, latent, or tertiary); query the provider for more specific information when possible to assign a more precise code
Ensure proper documentation of serological test results and clinical findings, as more specific syphilis codes (A50-A53.8) provide better clinical detail and may affect treatment decisions

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is A53.9 an HCC code?

No. A53.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

Code
A53.9
Description
Syphilis, unspecified
HCC (V28)
No CMS-HCC V28 mapping
RAF
—
Billable
Yes
Payment year
2026

Coder workflow notes

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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).

What This Code Means

A53.9 is the ICD-10-CM diagnosis code for syphilis, unspecified. This code is used when a patient has syphilis (a sexually transmitted bacterial infection) but the specific stage or type has not been determined or documented. Syphilis can affect multiple body systems and requires treatment with antibiotics. A53.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering infections with a predominantly sexual mode of transmission (a50-a64).

A53.9 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Use this code only when the documentation does not specify the stage of syphilis (primary, secondary, latent, or tertiary); query the provider for more specific information when possible to assign a more precise code.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A53.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code only when the documentation does not specify the stage of syphilis (primary, secondary, latent, or tertiary); query the provider for more specific information when possible to assign a more precise code
  • •Ensure proper documentation of serological test results and clinical findings, as more specific syphilis codes (A50-A53.8) provide better clinical detail and may affect treatment decisions

Excludes 1, Do NOT code together

  • syphilis NOS under two years of age (A50.2)

Child Codes

A53.0Latent syphilis, unspecified as early or late
A53.9Syphilis, unspecified

Code Hierarchy

└A53Other and unspecified syphilis└A53.9Syphilis, unspecified
└A53.9Syphilis, unspecified

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