2027 ICD-10-CM Diagnosis Code A53.9Syphilis, unspecified

ICD-10-CM Codes›A00–B99›A50-A64›A53

ICD-10-CM A53.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A53.9 is a billable ICD-10-CM diagnosis code for syphilis, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 867 through 869. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Sexually transmitted infections (excluding HIV and hepatitis).

Code Identity

ICD-10-CM Code
A53.9
Billable Status
Yes — Valid for Submission
Code Describes
Syphilis, unspecified
Short Description
Syphilis, unspecified
Same as the full description in the CMS dataset.
Parent Code
A53
Other and unspecified syphilis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA53Other and unspecified syphilis
This CodeA53.9Syphilis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired syphilis
  • Anetoderma
  • Anetoderma secondary to syphilis
  • Gingival disease caused by bacteria
  • Gingival disease caused by Treponema pallidum
  • Maternal syphilis during pregnancy, childbirth and the puerperium
  • Myelitis caused by bacterium
  • Myelitis caused by Treponema pallidum
  • Oral syphilis
  • Secondary anetoderma
  • Sexually transmitted infectious disease in mother complicating childbirth
  • Syphilis
  • Syphilis in mother complicating childbirth
  • Syphilis test finding
  • Treponema pallidum detected by enzyme-linked immunosorbent assay
  • Venereal disease in pregnancy

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A53.9: its own notes plus those printed at block A50-A64 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

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

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

On A53.9 itself
  • syphilis NOS under two years of age (A50.2)
From Block A50-A64 Infections with a predominantly sexual mode of transmission applies to 142 codes
  • nonspecific and nongonococcal urethritis (N34.1)
  • Reiter's disease (M02.3-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block A50-A64 Infections with a predominantly sexual mode of transmission applies to 142 codes
  • human immunodeficiency virus [HIV] disease (B20)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A53.9, its category, or a range that includes it.

Applicable To 1

These notes mention A53.9.

  • O98.1 Syphilis complicating pregnancy, childbirth and the puerperium
    Conditions in A50-A53 names A50-A53, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming A53.9: its condition is not part of those codes, and both may be reported when the patient has both.

  • Block A65-A69 Other spirochetal diseases
    syphilis (A50-A53) names A50-A53, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF010
Sexually transmitted infections (excluding HIV and hepatitis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Syphilis

    a contagious venereal disease caused by the spirochete treponema pallidum.

Patient EducationClinical

Syphilis

Syphilis is a sexually transmitted infection (STI) caused by bacteria. It infects the genital area, lips, mouth, or anus of both men and women. You usually get syphilis from sexual contact with someone who has it. It can also pass from mother to baby during pregnancy.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A53.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
097.9 Syphilis NOS
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A53.9Overview

What is the ICD-10 code for syphilis, unspecified?

The ICD-10-CM code for syphilis, unspecified is A53.9 (sometimes written as A539). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A53.9 (Other and unspecified syphilis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report syphilis, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does A53.9 group to?

When syphilis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 869, 868, with relative weights from 0.6784 to 2.1855 depending on complications. Higher weights mean higher Medicare reimbursement.

Can A53.9 be reported with A50.2?

Not as a rule. The Excludes1 note on A53.9 lists "syphilis NOS under two years of age (A50.2)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of A53.9?

Under the General Equivalence Mappings, syphilis, unspecified converts to ICD-9-CM 097.9 (syphilis NOS). The mapping is a direct match.