2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

L66.4 is a billable ICD-10-CM diagnosis code for folliculitis ulerythematosa reticulata. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to L66.4: its own notes plus those printed at block L60-L75 and Chapter 12. 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 Block L60-L75 Disorders of skin appendages applies to 85 codes
  • congenital malformations of integument (Q84.-)

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 Chapter 12 (L00-L99) Diseases of the skin and subcutaneous tissue applies to 1,001 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • lipomelanotic reticulosis (I89.8)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • viral warts (B07.-)

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

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 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About L66.4Overview

What is the ICD-10 code for folliculitis ulerythematosa reticulata?

The ICD-10-CM code for folliculitis ulerythematosa reticulata is L66.4 (sometimes written as L664). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 607, 606, with relative weights from 0.8772 to 1.5721 depending on complications. Higher weights mean higher Medicare reimbursement.

Can L66.4 be reported with a code from Q84?

Not as a rule. The Excludes1 note at block L60-L75, which applies to L66.4, lists "congenital malformations of integument (Q84.-)". 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).

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.