2026 ICD-10-CM Diagnosis Code A56.4Chlamydial infection of pharynx

ICD-10-CM Codes›A00–B99›A50-A64›A56

ICD-10-CM A56.4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A56.4 is a billable ICD-10-CM diagnosis code for chlamydial infection of pharynx. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 152 through 153. Coders also document this condition as chlamydial pharyngitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified upper respiratory infections and Sexually transmitted infections (excluding HIV and hepatitis).

Code Identity

ICD-10-CM Code
A56.4
Billable Status
Yes — Valid for Submission
Code Describes
Chlamydial infection of pharynx
Short Description
Chlamydial infection of pharynx
Same as the full description in the CMS dataset.
Parent Code
A56
Other sexually transmitted chlamydial diseases

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA50-A64Infections with a predominantly sexual mode of transmission
CategoryA56Other sexually transmitted chlamydial diseases
This CodeA56.4Chlamydial infection of pharynx

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chlamydial pharyngitis
  • Infection of pharynx caused by Chlamydia trachomatis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Chlamydia, chlamydial
      • pharyngitis
    • Disease, diseased
      • venereal
        • chlamydial NEC
          • pharynx
    • Infection, infected, infective(opportunistic)
      • Chlamydia, chlamydial
        • pharynx
    • Pharyngitis(acute) (catarrhal)(gangrenous) (infective) (malignant) (membranous) (phlegmonous) (pseudomembranous) (simple) (subacute) (suppurative) (ulcerative) (viral)
      • chlamydial

Clinical ClassificationClinical

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

CCSR RSP006
Other specified upper respiratory infections
Default principal diagnosis: inpatient No · outpatient No
CCSR INF010
Sexually transmitted infections (excluding HIV and hepatitis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Chlamydia Infections

Chlamydia is a common sexually transmitted infection (STI). It is caused by bacteria called Chlamydia trachomatis. Anyone can get chlamydia. It often doesn't cause symptoms, so people may not know that they have it. Antibiotics can cure it. But if it's not treated, chlamydia can cause serious health problems.

The full article covers:

  • What is chlamydia?
  • How is chlamydia spread?
  • Who is more likely to get chlamydia?
  • What are the symptoms of chlamydia?
  • How is chlamydia diagnosed?
  • Who should be tested for chlamydia?
  • What other problems can chlamydia cause?
  • What are the treatments for chlamydia?

Read the full article at MedlinePlus

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

Convert A56.4 to ICD-9-CMHistory

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

ICD-9-CM
099.51 Oth VD chlm trch pharynx
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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A56.4Overview

Is A56.4 (Other sexually transmitted chlamydial diseases) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chlamydial infection of pharynx on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A56.4 group to?

When chlamydial infection of pharynx is the principal diagnosis on an inpatient stay, it groups to MS-DRG 152, 153, with relative weights from 0.7382 to 1.1822 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A56.4?

Under the General Equivalence Mappings, chlamydial infection of pharynx converts to ICD-9-CM 099.51 (oth VD chlm trch pharynx). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.