2026 ICD-10-CM Diagnosis Code S90.426ABlister (nonthermal), unspecified lesser toe(s), initial encounter

ICD-10-CM Codes›S00–T88›S90-S99›S90

ICD-10-CM S90.426A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S90.426A is a billable ICD-10-CM diagnosis code for blister (nonthermal), unspecified lesser toe(s), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. 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, 963 through 965. Coders also document this condition as blister of foot with infection. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Superficial injury; contusion, initial encounter.

Code Identity

ICD-10-CM Code
S90.426A
Billable Status
Yes — Valid for Submission
Code Describes
Blister (nonthermal), unspecified lesser toe(s), initial encounter
Short Description
Blister (nonthermal), unspecified lesser toe(s), init encntr
Parent Code
S90.426
Blister (nonthermal), unspecified lesser toe(s)

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS90-S99Injuries to the ankle and foot
CategoryS90Superficial injury of ankle, foot and toes
This CodeS90.426ABlister (nonthermal), unspecified lesser toe(s), initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Blister of foot with infection
  • Blister of foot without infection
  • Blister of toe with infection
  • Blister of toe without infection
  • Traumatic blister of foot, infected
  • Traumatic blister of lesser toe
  • Traumatic blister of toe
  • Traumatic blister of toe, infected

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Superficial injury of ankle, foot and toes (S90). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

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

CCSR INJ017
Superficial injury; contusion, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Blister

    visible accumulations of fluid within or beneath the epidermis.

  • Herpes Labialis

    herpes simplex, caused by type 1 virus, primarily spread by oral secretions and usually occurring as a concomitant of fever. it may also develop in the absence of fever or prior illness. it commonly involves the facial region, especially the lips and the nares. (dorland, 27th ed.)

Patient EducationClinical

Blisters

Blisters are fluid-filled sacs on the outer layer of your skin. They form because of rubbing, heat, or diseases of the skin. They are most common on your hands and feet.

The full article covers:

  • What are blisters?
  • What causes blisters?
  • What are the treatments for blisters?
  • Can blisters be prevented?

Read the full article at MedlinePlus

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

Convert S90.426A to ICD-9-CMHistory

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

ICD-9-CM
917.2 Blister foot & toe
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 S90.426AOverview

Is S90.426A (Blister (nonthermal), unspecified lesser toe(s)) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report blister (nonthermal), unspecified lesser toe(s), initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in S90.426A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for blister (nonthermal), unspecified lesser toe(s), such as an emergency visit or first evaluation.

What MS-DRG does S90.426A group to?

When blister (nonthermal), unspecified lesser toe(s), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, 963, 964, 965, with relative weights from 0.9064 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of S90.426A?

Under the General Equivalence Mappings, blister (nonthermal), unspecified lesser toe(s), initial encounter converts to ICD-9-CM 917.2 (blister foot & toe). 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.