2027 ICD-10-CM Diagnosis Code Q18.5Microstomia

ICD-10-CM Codes›Q00-Q99›Q10-Q18›Q18

ICD-10-CM Q18.5
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q18.5 is a billable ICD-10-CM diagnosis code for microstomia. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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 the other POA exempt codes in Congenital malformations of eye, ear, face and neck (Q10-Q18).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Flat face, microstomia, ear anomaly syndrome
  • Microstomia

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q18.5: its own notes plus those printed at Q18, block Q10-Q18, and Chapter 17. A note printed at a category, block or chapter applies to every code under it.

Excludes1

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

From Q18 Other congenital malformations of face and neck applies to 10 codes
  • cleft lip and cleft palate (Q35-Q37)
  • conditions classified to Q67.0-Q67.4
  • congenital malformations of skull and face bones (Q75.-)
  • cyclopia (Q87.0)
  • dentofacial anomalies [including malocclusion] (M26.-)
  • malformation syndromes affecting facial appearance (Q87.0)
  • persistent thyroglossal duct (Q89.2)

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 Q10-Q18 Congenital malformations of eye, ear, face and neck applies to 62 codes
  • cleft lip and cleft palate (Q35-Q37)
  • congenital malformation of cervical spine (Q05.0, Q05.5, Q67.5, Q76.0-Q76.4)
  • congenital malformation of larynx (Q31.-)
  • congenital malformation of lip NEC (Q38.0)
  • congenital malformation of nose (Q30.-)
  • congenital malformation of parathyroid gland (Q89.2)
  • congenital malformation of thyroid gland (Q89.2)
From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • inborn errors of metabolism (E70-E88)

Notes

General instructions on how these codes are used.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • Codes from this chapter are not for use on maternal records

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Q18.5, its category, or a range that includes it.

Excludes1 2

These codes carry an Excludes1 note naming Q18.5: they are not reported together with it, unless the two conditions are unrelated.

  • Q38 Other congenital malformations of tongue, mouth and pharynx
    microstomia (Q18.5)
  • Q75 Other congenital malformations of skull and face bones
    congenital malformation of face NOS (Q18.-) names Q18.-, 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 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Q18.5Overview

What is the ICD-10 code for microstomia?

The ICD-10-CM code for microstomia is Q18.5 (sometimes written as Q185). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does Q18.5 group to?

When microstomia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 159, 158, 157, with relative weights from 0.6890 to 1.8082 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. The code appears in the Congenital malformations of eye, ear, face and neck (Q10-Q18) range of the CMS exempt list.

Can Q18.5 be reported with a code from Q75?

Not as a rule. The Excludes1 note at Q18, which applies to Q18.5, lists "congenital malformations of skull and face bones (Q75.-)". 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).