Abstract
Background. In idiopatic pulmonary fibrosis (IPF) the progression of the disease can be slow or rapid and the rate of progression strongly influences prognosis. Variations in MUC5B promoter, resulting in a variable increase in mucin expression, have been associated with IPF. It is not known if mucus production could be related to the rate of FVC decay.
Aims: 1)To quantify mucus content in severe IPF lungs and to investigate its relation to rate of FVC decline (rapid or slow) and lung inflammation; 2)To compare mucus content in IPF with severe COPD.
Methods. Explanted lungs of 14 IPF patients (age:55±10) classified as slow or rapid progressors based on yearly FVC decline (<or>10%predicted) were studied. 7 severe COPD explanted lungs and 7 healthy donors lungs were included for comparison. Mucus content was quantified by point counting in Periodic Schiff stained sections. Inflammation was quantified by immunohistochemistry.
Results. The volume fraction of mucus in IPF (median;range 2.1;0.4-10.6%) was increased compared to donors (0;0-0.2%;p<0005) and COPD subjects (0.4;0.2-1.1%;p<0.005). Mucus content in COPD subjects was increased compared to donors (p=0.001). When IPF patients were stratified by FVC decline, the mucus content of rapid progressors was twice that present in slow progressors (3.5;1-10.6vs1.4;0.4-10%), but did not reach statistical significance. In IPF lungs mucus content correlated positively with the number of lymphocytes, particularly B (p<0.05,r=0.61) and C8+(p<0.05,r=0.64).
Conclusions. A prominent mucus production is a distinct finding in the lungs of patients with severe IPF, even surpassing the amount in lungs with COPD. The mucus content paralleled the degree of lung inflammation and FVC decline.
- © 2014 ERS