Respiratory bronchiolitis-interstitial lung disease

Respiratory bronchiolitis interstitial lung disease (RB-ILD) is the symptomatic form of smoking related interstitial lung disease in the same spectrum as respiratory bronchiolitis (RB), but demonstrating more severe histological findings. On CT, the appearances should be reported as RB.

Epidemiology

In almost all cases, respiratory bronchiolitis-interstitial lung disease is associated with heavy tobacco smoking (usually 30 pack-years or more) and is often seen in 30-40 years age group.

Clinical presentation

Chronic cough and progressive dyspnea ⁴ differentiate RB-ILD from RB. Inspiratory crackles are heard in up to half of patients. Clubbing is rare ¹. RB-ILD is a clinical diagnosis.

Pathology

On lung biopsy of respiratory bronchiolitis-interstitial lung disease, pigment-laden macrophages are found within alveoli, and peribronchial inflammation noted. Unlike simple respiratory bronchiolitis, fibrosis extends beyond the tissues immediately adjacent to respiratory bronchioles and extends into alveolar septae.

Histologically respiratory bronchiolitis-interstitial lung disease is very similar to desquamative interstitial pneumonia (DIP) and many authors feel that the two conditions are closely related, or even variants of the same condition ³. It has even been suggested that DIP should be abolished altogether, and simply thought of as end-stage/severe RB-ILD ⁵.

Radiographic features

CT

• ground glass opacities: may have a slight upper zone predilection ⁹

• poorly defined centrilobular nodules

• no particular distribution with both upper and lower zones potentially affected

• if advanced, fibrosis may be evident typically affecting the subpleural regions and more so in the lower lung zones

• patchy areas of hypoattenuation (~40%) with a lower lung predominance ¹⁰

• other changes related to smoking

  • bronchial wall thickening: can be central +/- peripheral

  • centrilobular emphysema

Treatment and prognosis

Usually, no treatment is required for respiratory bronchiolitis-interstitial lung disease other than giving up smoking.

History and etymology

It was first described in 1974 by the American pulmonologist Dennis E Niewoehner (1940-2020) ¹⁵ and colleagues ^11,13.

Differential diagnosis

With typical HRCT chest appearances consider:

• non-specific interstitial pneumonitis (NSIP)

  • changes of fibrosis: lung volume loss, reticular opacities, and traction bronchiectasis

  • ground glass opacities have a random distribution

• non-fibrotic or fibrotic hypersensitivity pneumonitis (HP)

See also

• smoking-related lung disease