2026 ICD-10-CM Diagnosis Code J21.9Acute bronchiolitis, unspecified

ICD-10-CM Codes›J00–J99›J20-J22›J21

ICD-10-CM J21.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J21.9 is a billable ICD-10-CM diagnosis code for acute bronchiolitis, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 202 through 203. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute bronchitis.

Code Identity

ICD-10-CM Code
J21.9
Billable Status
Yes — Valid for Submission
Code Describes
Acute bronchiolitis, unspecified
Short Description
Acute bronchiolitis, unspecified
Same as the full description in the CMS dataset.
Parent Code
J21
Acute bronchiolitis

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ20-J22Other acute lower respiratory infections
CategoryJ21Acute bronchiolitis
This CodeJ21.9Acute bronchiolitis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute bronchiolitis
  • Acute bronchiolitis with bronchospasm
  • Acute bronchiolitis with obstruction
  • Acute bronchitis with bronchospasm
  • Acute bronchospasm
  • Acute exudative bronchiolitis
  • Acute obliterating bronchiolitis
  • Acute viral bronchiolitis
  • Bronchiolitis
  • Bronchiolitis exudativa
  • Bronchospasm
  • Chronic bronchiolitis
  • Diffuse panbronchiolitis
  • Necrotizing bronchiolitis
  • Pulmonary necrosis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Bronchiolitis (acute)

Type 1 Excludes

  • chronic bronchiolitis J44.89

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.

    • Bronchiolitis(acute) (infective) (subacute)
    • Bronchiolitis(acute) (infective) (subacute)
      • with
        • bronchospasm or obstruction
    • Bronchospasm(acute)
      • with
        • bronchiolitis, acute

Clinical ClassificationClinical

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

CCSR RSP005
Acute bronchitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Bronchiolitis

    inflammation of the bronchioles.

  • Bronchiolitis Obliterans

    inflammation of the bronchioles leading to an obstructive lung disease. bronchioles are characterized by fibrous granulation tissue with bronchial exudates in the lumens. clinical features include a nonproductive cough and dyspnea.

  • Bronchiolitis Obliterans Syndrome

    bronchiolitis obliterans complication from allogenic hematopoietic stem cell transplantation and lung transplantation.

  • Bronchiolitis, Viral

    an acute inflammatory disease of the lower respiratory tract, caused by paramyxoviruses, occurring primarily in infants and young children; the viruses most commonly implicated are parainfluenza virus type 3; respiratory syncytial virus, human; and metapneumovirus.

  • Cryptogenic Organizing Pneumonia

    an interstitial lung disease of unknown etiology, occurring between 21-80 years of age. it is characterized by a dramatic onset of a pneumonia-like illness with cough, fever, malaise, fatigue, and weight loss. pathological features include prominent interstitial inflammation without collagen fibrosis, diffuse fibroblastic foci, and no microscopic honeycomb change. there is excessive proliferation of granulation tissue within small airways and alveolar ducts.

  • Bronchioles

    the small airways branching off the tertiary bronchi. terminal bronchioles lead into several orders of respiratory bronchioles which in turn lead into alveolar ducts and then into pulmonary alveoli.

  • Acute Bronchiolitis

    acute inflammation of the bronchioles usually caused by the respiratory syncytial virus.

  • Bronchospasm

    sudden contraction of the smooth muscles of the bronchial wall.

  • Bronchospasm, CTCAE|Bronchospasm|Bronchospasm

    a disorder characterized by a sudden contraction of the smooth muscles of the bronchial wall.

  • Exercise-Induced Bronchospasm|Exercise induced bronchospasm

    sudden contraction of the smooth muscles of the bronchial wall that occurs during or following exercise.

  • Grade 1 Bronchospasm, CTCAE|Grade 1 Bronchospasm

    mild symptoms; intervention not indicated

  • Grade 2 Bronchospasm, CTCAE|Grade 2 Bronchospasm

    symptomatic; medical intervention indicated; limiting instrumental adl

  • Grade 3 Bronchospasm, CTCAE|Grade 3 Bronchospasm

    limiting self care adl; supplemental oxygen indicated

  • Grade 4 Bronchospasm, CTCAE|Grade 4 Bronchospasm

    life-threatening respiratory or hemodynamic compromise; intubation or urgent intervention indicated

  • Grade 5 Bronchospasm, CTCAE|Grade 5 Bronchospasm

    death

  • Diffuse Panbronchiolitis

    a clinico-pathologic syndrome primarily affecting the respiratory bronchioles with evidence of inflammation in all layers of the bronchiole. sinusitis is often an accompanying feature.

  • Bronchospasm, CTCAE|Bronchospasm|Bronchospasm

    a disorder characterized by a sudden contraction of the smooth muscles of the bronchial wall or narrowing of the airway. may be manifested as wheezing.

  • Grade 2 Bronchospasm, CTCAE|Grade 2 Bronchospasm

    symptomatic; medical intervention indicated; limiting instrumental adl or mild/moderate impact on age-appropriate normal daily activity (pediatric)

  • Grade 3 Bronchospasm, CTCAE|Grade 3 Bronchospasm

    supplemental oxygen indicated; limiting self-care adl or severe impact on age-appropriate normal daily activity (pediatric)

Patient EducationClinical

Bronchial Disorders

When you breathe in, the air travels down through your trachea (windpipe). It then goes through two tubes to your lungs. These tubes are your bronchi. Bronchial disorders can make it hard for you to breathe.

Read the full article at MedlinePlus

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

Convert J21.9 to ICD-9-CMHistory

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

ICD-9-CM
466.19 Acu brnchlts d/t oth org
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 J21.9Overview

Is J21.9 (Acute bronchiolitis) a billable code?

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

What MS-DRG does J21.9 group to?

When acute bronchiolitis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 202, 203, with relative weights from 0.6700 to 0.9712 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of J21.9?

Under the General Equivalence Mappings, acute bronchiolitis, unspecified converts to ICD-9-CM 466.19 (acu brnchlts d/t oth org). 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.