2026 ICD-10-CM Diagnosis Code L66.4Folliculitis ulerythematosa reticulata

ICD-10-CM Codes›L00–L99›L60-L75›L66

ICD-10-CM L66.4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

L66.4 is a billable ICD-10-CM diagnosis code for folliculitis ulerythematosa reticulata. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 606 through 607. Coders also document this condition as atrophoderma vermiculatum. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified skin disorders.

Code Identity

ICD-10-CM Code
L66.4
Billable Status
Yes — Valid for Submission
Code Describes
Folliculitis ulerythematosa reticulata
Short Description
Folliculitis ulerythematosa reticulata
Same as the full description in the CMS dataset.
Parent Code
L66
Cicatricial alopecia [scarring hair loss]

Code Classification

ChapterL00–L99Diseases of the skin and subcutaneous tissue
SectionL60-L75Disorders of skin appendages
CategoryL66Cicatricial alopecia [scarring hair loss]
This CodeL66.4Folliculitis ulerythematosa reticulata

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Atrophoderma vermiculatum
  • Keratosis pilaris
  • Keratosis pilaris atrophicans

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.

    • Atrophoderma, atrophodermia(of)
      • reticulatum symmetricum faciei
    • Atrophoderma, atrophodermia(of)
      • vermiculata (cheeks)
    • Folliculitis(superficial)
      • ulerythematosa reticulata

Clinical ClassificationClinical

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

CCSR SKN007
Other specified and unspecified skin disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Hair Loss

You lose up to 100 hairs from your scalp every day. That's normal, and in most people, those hairs grow back. But many men -- and some women -- lose hair as they grow older. You can also lose your hair if you have certain diseases, such as thyroid problems, diabetes, or lupus.

Read the full article at MedlinePlus

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

Convert L66.4 to ICD-9-CMHistory

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

ICD-9-CM
701.8 Skin hypertro/atroph NEC
Approximate The match is approximate rather than exact.

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 L66.4Overview

Is L66.4 (Cicatricial alopecia [scarring hair loss]) a billable code?

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

What MS-DRG does L66.4 group to?

When folliculitis ulerythematosa reticulata is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, with relative weights from 0.9064 to 1.5132 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of L66.4?

Under the General Equivalence Mappings, folliculitis ulerythematosa reticulata converts to ICD-9-CM 701.8 (skin hypertro/atroph NEC). The mapping is approximate, so confirm the match fits the documentation.

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.