Constrictive Bronchiolitis

Constrictive bronchiolitis presents an important split between service connection and rating. 38 U.S.C. § 1120 specifically lists constrictive bronchiolitis or obliterative bronchiolitis as presumptive for a covered veteran. But current 38 CFR Part 4 does not provide a dedicated diagnostic code for the disease.

That means the PACT Act may establish the nexus while VA must still choose an analogous rating under 38 CFR § 4.20. No website can assign every veteran DC 6600, DC 6604, or another fixed code in advance. The analogy must fit the functions affected, anatomy, and symptom pattern shown by the individual record.

TL;DR

• Constrictive bronchiolitis and obliterative bronchiolitis are listed in 38 U.S.C. § 1120 as PACT Act presumptive diseases for covered veterans.
• The current VA rating schedule has no dedicated constrictive-bronchiolitis diagnostic code.
• VA may rate an unlisted disease by analogy under § 4.20, but it must explain why the selected code is closely related.
• Respiratory analogies may use pulmonary-function results or other findings, depending on the code VA selects.
• Normal or mildly abnormal spirometry does not automatically exclude small-airway disease or measure all exertional impairment.
• The diagnosis and the rating are separate: qualifying service can establish the presumption, but medical evidence still determines severity.
• Overlapping respiratory conditions generally cannot receive duplicate ratings for the same impairment under § 4.96.
• No verified aggregate Board-outcome dataset specific to constrictive bronchiolitis was available, so this page publishes no grant-rate statistic.

PACT Act Presumptive Service Connection

Section 1120 lists “constrictive bronchiolitis or obliterative bronchiolitis.” The presumption applies when the disease becomes manifest in a covered veteran. Section 1119 supplies the specific covered locations and periods.

A presumptive packet should include:

• service records showing a qualifying location and period;
• the current pulmonary diagnosis and supporting studies; and
• evidence of present functional and respiratory impairment.

Do not reduce the rule to “any burn-pit exposure qualifies.” The statutory covered-service definition controls. Veterans outside that definition may still pursue direct service connection.

No Dedicated Diagnostic Code

Part 4 lists chronic bronchitis, emphysema, COPD, interstitial lung disease, and other respiratory diagnoses, but it does not list constrictive bronchiolitis by name. Section 4.20 allows an unlisted condition to be rated under a closely related disease or injury with similar functions, anatomy, and symptoms. It also warns against conjectural analogies.

Possible respiratory analogies may include chronic bronchitis or another code whose criteria match the measured disease. The selected code is not automatic. If VA uses DC 6600, it should explain why the chronic-bronchitis framework fits. If another code is used, the decision should identify the medical and functional match.

The code matters because different formulas emphasize different tests. Review the rating decision and examination rather than assuming the percentage from the diagnosis name.

Diagnosis and Why Routine Testing Can Miss It

Constrictive bronchiolitis is a small-airway disease. Veterans may report exertional shortness of breath, dry cough, chest tightness, and reduced exercise tolerance. Routine chest imaging can be unrevealing, and spirometry may not fully describe exercise limitation in every case.

Depending on the clinical record, evaluation may include:

• full pulmonary-function testing with lung volumes and diffusion capacity;
• inspiratory and expiratory high-resolution CT;
• exercise testing;
• evaluation for asthma, COPD, vocal-cord dysfunction, cardiac disease, and other alternatives; and
• lung biopsy when clinically appropriate.

Claim Raven does not recommend an invasive test. The treating pulmonologist should decide which procedures are medically justified. A claim should report the diagnostic evidence that actually exists and should not describe biopsy as mandatory when the clinician established the diagnosis another way.

Direct Service Connection

When the statutory presumption does not apply, 38 CFR § 3.303 permits a direct claim. Useful evidence may include documented exposure, onset and progression of exertional symptoms, pulmonary evaluations, and a medical opinion explaining why the veteran's disease is at least as likely as not related to service.

A toxic-exposure risk activity finding supports the exposure element. It does not replace the diagnosis or the medical nexus when the disease is not presumptive for that veteran.

Rating Evidence

Because there is no dedicated code, submit evidence broad enough to support the correct analogy:

• the exact diagnosis and differential workup;
• complete PFT values, including whether results are pre- or post-bronchodilator;
• CT and exercise-test findings;
• oxygen use, respiratory failure, pulmonary hypertension, or cor pulmonale when present;
• treatment and response;
• walking, stair, lifting, and work limitations; and
• evidence distinguishing the disability from separately diagnosed asthma, COPD, or cardiac disease.

Section 4.96 generally prevents combining ratings for overlapping respiratory diagnoses within specified code ranges. VA should assign the code reflecting the predominant disability, with elevation in the circumstances described by the regulation, rather than duplicate the same reduced pulmonary function.

Common Failure Modes

• Treating the PACT Act presumption as a dedicated rating code.
• Calling DC 6600 the universal constrictive-bronchiolitis code.
• Relying on one normal chest X-ray or spirometry result without the full pulmonary assessment.
• Claiming every exercise limitation is pulmonary without addressing cardiac or other causes.
• Seeking separate ratings for multiple respiratory labels that produce the same impairment.

Bottom Line

Constrictive bronchiolitis has a strong statutory service-connection route for covered veterans and an unsettled rating route because no dedicated code exists. Prove qualifying service, preserve the exact diagnosis, and require the decision to explain the analogy it selects. The percentage must follow the veteran's measured respiratory disability, not a generic code assigned by an article.

Legal sources: 38 U.S.C. § 1119, 38 U.S.C. § 1120, 38 CFR § 4.20, § 4.96, and § 3.303, checked August 13, 2026.