2026 ICD-10-CM Diagnosis Code K12.0Recurrent oral aphthae

ICD-10-CM Codes›K00–K95›K00-K14›K12

ICD-10-CM K12.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K12.0 is a billable ICD-10-CM diagnosis code for recurrent oral aphthae. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 157 through 159. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Any dental condition including traumatic injury, Diseases of mouth; excluding dental, and Nontraumatic dental conditions.

Code Identity

ICD-10-CM Code
K12.0
Billable Status
Yes — Valid for Submission
Code Describes
Recurrent oral aphthae
Short Description
Recurrent oral aphthae
Same as the full description in the CMS dataset.
Parent Code
K12
Stomatitis and related lesions

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK00-K14Diseases of oral cavity and salivary glands
CategoryK12Stomatitis and related lesions
This CodeK12.0Recurrent oral aphthae

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abrasion of hard palate
  • Abrasion of palate
  • Aphthae major
  • Aphthous ulcer of mouth
  • Aphthous ulceration of skin and/or mucous membrane
  • Bednar's aphthae
  • Cervical lymphadenitis
  • Complex multigenic autoinflammatory syndrome
  • Herpetiform aphthous stomatitis
  • MAGIC syndrome
  • Minor oral aphthous ulceration
  • PFAPA syndrome
  • Recurrent aphthous stomatitis
  • Recurrent aphthous ulcer
  • Recurrent ulcer of mouth
  • Superficial injury of palate
  • Traumatic oral ulceration
  • Traumatic ulcer of oral mucosa

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Aphthous stomatitis (major) (minor)
  • Bednar's aphthae
  • Periadenitis mucosa necrotica recurrens
  • Recurrent aphthous ulcer
  • Stomatitis herpetiformis

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.

    • Aphthae, aphthous
      • Bednar's
    • Aphthae, aphthous
      • oral (recurrent)
    • Aphthae, aphthous
      • stomatitis (major) (minor)
    • Aphthae, aphthous
      • ulcer (oral) (recurrent)
    • Bednar's
      • aphthae
    • Canker(mouth) (sore)
    • Periadenitis mucosa necrotica recurrens
    • Sore
      • mouth
        • canker
    • Stomatitis(denture) (ulcerative)
      • aphthous
    • Stomatitis(denture) (ulcerative)
      • herpetiformis
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • aphthous (oral) (recurrent)

Clinical ClassificationClinical

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

CCSR DEN001
Any dental condition including traumatic injury
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG003
Diseases of mouth; excluding dental
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR DEN002
Nontraumatic dental conditions
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Cervical Lymphadenitis

    inflammation of the cervical lymph nodes.

Patient EducationClinical

Mouth Disorders

Your mouth is one of the most important parts of your body. It has many different functions. It allows you to:

Read the full article at MedlinePlus

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

Convert K12.0 to ICD-9-CMHistory

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

ICD-9-CM
528.2 Oral aphthae
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 K12.0Overview

Is K12.0 (Stomatitis and related lesions) a billable code?

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

What MS-DRG does K12.0 group to?

When recurrent oral aphthae is the principal diagnosis on an inpatient stay, it groups to MS-DRG 157, 158, 159, with relative weights from 0.7085 to 1.7168 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K12.0?

Under the General Equivalence Mappings, recurrent oral aphthae converts to ICD-9-CM 528.2 (oral aphthae). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.