Respiratory Bronchiolitis Interstitial Lung Disease – is it more common than we thought?

Title: Respiratory Bronchiolitis Interstitial Lung Disease – is it more common than we thought?
Author(s): C Cruickshank, M Donaghy, E Murtagh, P Minnis.
Institution: Northern Trust Antrim Area Hospital Interstitial Lung Disease Service, Northern Ireland
Poster: Click to view poster
Category: ILD
Abstract: Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) is a rare, inflammatory pulmonary disorder that occurs almost exclusively in current or former heavy smokers. A previous epidemiological study has reported the incidence of 0.04 per 100,000.1 The natural history is unknown, specifically whether interventions result in radiological or clinical improvement and what the long-term sequelae may be of this condition.

We reviewed all patients attending ILD clinic (712) over the last 18 months and identified 23 (3.2%) with RB-ILD satisfying clinic-radiological descriptors in addition to pathology where available. The crude incidence was estimated at 4.86 per 100,000. The average age at presentation was 56.1 years (35-77) having accrued 40.2 pack years and demonstrated a slight female predominance (12/23). All but one patient reported gradual onset of exertional dyspnoea, symptomatic wheeze and or persistent cough. In all cases high resolution computed tomography (HRCT) described centrilobular micronodules, ground-glass opacities, and peribronchiolar thickening. Additional emphysema was seen in 6/23. 11 patients underwent bronchoscopy for confirmatory pathology.

21 patients had serial data and were followed up for a median of 38.7 months (IQR 14.2-58.3). During this time 7 stop smoking, 6 reduced consumption and the rest continued actively smoking. Radiological improvement was seen in 2 patients both of which had stopped smoking. Adjusted DLCO percentage change was calculated for a 24-month period with patients characterised into “active”, “reduced” and “stopped” tobacco use cohorts (Fig 1). There was a small signal in terms of the relationship of ESR with DLCO when adjusted for co-existent emphysema.

A higher incidence than expected within the Northern Trust was identified. Active tobacco use was associated, not surprisingly to a greater percentage decline in DLCO over 24 months. Ongoing follow up of this cohort will be useful in identifying possible long-term sequelae particularly in terms of relationship to other interstitial pneumonias.