Alphabetic Index FY2027

J21.9

Acute bronchiolitis, unspecified

FY2027Chapter 10: Diseases of the respiratory system/J20–J22 Other acute lower respiratory infections

BillableComplete code, valid to report
Care settingsHome Health Primary · MMTA - RespiratoryHospital CC

J21.9 (also written J219) is a billable ICD-10-CM diagnosis code for acute bronchiolitis, unspecified. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 4 codes in category J21 (Acute bronchiolitis). The Alphabetic Index lists it under 3 entries. Its coding notes include a Use additional code instruction, 1 Excludes1 entry and 11 Excludes2 entries.

Use additional code

Add the listed code as a secondary code, if known.

Also from chapter/block level (7 notes)
Inherited from Chapter 10 Diseases of the respiratory system
  • code, where applicable, to identify:
    • exposure to environmental tobacco smoke (Z77.22)
    • exposure to tobacco smoke in the perinatal period (P96.81)
    • history of tobacco dependence (Z87.891)
    • occupational exposure to environmental tobacco smoke (Z57.31)
    • tobacco dependence (F17.-)
    • tobacco use (Z72.0)

Excludes1

Not coded here. The listed conditions generally should not be reported together.

This code
  • chronic bronchiolitis (J44.89)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Inherited from J21 Acute bronchiolitis
  • respiratory bronchiolitis interstitial lung disease (J84.115)
Also from chapter/block level (10 notes)
Inherited from J20–J22 Other acute lower respiratory infections
  • chronic obstructive pulmonary disease with acute lower respiratory infection (J44.0)
Inherited from Chapter 10 Diseases of the respiratory system
  • 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)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • smoke inhalation (T59.81-)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Home Health Primary

Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Respiratory clinical group.

Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026

Hospital CC

Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 14 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.

Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix C

Includes

Further defines or gives examples of the content of the category.

Inherited from J21 Acute bronchiolitis
  • acute bronchiolitis with bronchospasm

Inclusion terms

Conditions classified to this code.

This code
  • Bronchiolitis (acute)

Notes

Also from chapter/block level (1 note)
Inherited from Chapter 10 Diseases of the respiratory system
  • When a respiratory condition is described as occurring in more than one site and is not specifically indexed, it should be classified to the lower anatomic site (e.g. tracheobronchitis to bronchitis in J40).

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 3 entries