2026 ICD-10-CM Diagnosis Code Q18.5Microstomia

ICD-10-CM Codes›Q00-Q99›Q10-Q18›Q18

ICD-10-CM Q18.5
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q18.5 is a billable ICD-10-CM diagnosis code for microstomia. 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. The code is exempt from POA reporting. Coders also document this condition as flat face, microstomia, ear anomaly syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Congenital malformations of eye, ear, face, neck.

Code Identity

ICD-10-CM Code
Q18.5
Billable Status
Yes — Valid for Submission
Code Describes
Microstomia
Short Description
Microstomia
Same as the full description in the CMS dataset.
Parent Code
Q18
Other congenital malformations of face and neck

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ10-Q18Congenital malformations of eye, ear, face and neck
CategoryQ18Other congenital malformations of face and neck
This CodeQ18.5Microstomia

Present on Admission (POA)Billing

Q18.5 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Flat face, microstomia, ear anomaly syndrome
  • Microstomia

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.

    • Microstomia(congenital)

Clinical ClassificationClinical

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

CCSR MAL005
Congenital malformations of eye, ear, face, neck
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Microstomia

    a congenital defect in which the mouth is unusually small. (dorland, 27th ed)

Patient EducationClinical

Craniofacial Abnormalities

Craniofacial is a medical term that relates to the bones of the skull and face. Craniofacial abnormalities are birth defects of the face or head. Some, like cleft lip and palate, are among the most common of all birth defects. Others are very rare. Most of them affect how a person's face or head looks.

Read the full article at MedlinePlus

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

Convert Q18.5 to ICD-9-CMHistory

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

ICD-9-CM
744.84 Microstomia
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 Q18.5Overview

Is Q18.5 (Other congenital malformations of face and neck) a billable code?

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

What MS-DRG does Q18.5 group to?

When microstomia 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.

Is Q18.5 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for microstomia on inpatient claims.

What is the ICD-9 equivalent of Q18.5?

Under the General Equivalence Mappings, microstomia converts to ICD-9-CM 744.84 (microstomia). 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.