A Case-Series of Biopsy-Proven Hypersensitivity Pneumonitis in Scotland
JE Pearce, WL Liou, WAH Wallace, J Murchison, P McFarlane, N Hirani, AJ Simpson.
Department of Respiratory Medicine, The Royal Infirmary of Edinburgh, EH16 4SA.
Hypersensitivity pneumonitis (HP) is an immune-mediated disease due to repeated exposure to a
sensitising antigen. It is now recognised that a diagnosis of HP can be made without a proven
causative agent. This study aimed to define the clinical features and causes in all cases of
biopsy-proven HP diagnosed at the Royal Infirmary of Edinburgh (RIE) from 1997 to 2007.
69 consecutive cases of HP were identified from the lung pathology archive at the RIE. A full data
set was available for 38 patients (3 transbronchial, 35 surgical biopsies). The following data was
recorded: Demographics, presenting signs and symptoms, radiological appearance, pulmonary
function tests (PFTs), bloods, exposure history, medical history, treatment and response to
There were 21 males (55%) and 17 (45%) females in the study group. The mean age was 58.7
years (range 29 – 74 years). Only 2 patients (5%) were current smokers. The most common
presenting symptoms were dyspnoea (92%) and cough (89%). The commonest clinical sign was
crackles on chest auscultation (88%). Ground glass attenuation was the commonest appearance
on HRCT (77%). A restrictive defect was identified in 19 (54%), an obstructive defect in 5 (15%)
and normal spirometry in 10 cases (29%). There was a diffusion defect in 90% of the 30 patients
tested. A cause, based on history of exposure and positive serum precipitin test, was identified in
11 cases (29%). A presumed cause, based on exposure history alone, was identified in 12 cases
(32%). In 15 cases (39%, 12 female, 4 male) no causative agent was identified. The most
common cause was exposure to avian antigens. Steroids were commenced in 30 patients. In 19
(63%) of these cases PFTs improved and 22 patients (73%) reported symptomatic benefit.
In this case-series of biopsy-proven HP a causative agent was not identified in a large number of
patients. Current approaches for identifying hidden causes of HP may be insufficient.