Causes of Idiopathic Pulmonary Fibrosis (IPF)
Ulrich Costabel discusses the possible causes of IPF
So the question is “What causes IPF?”.
By definition IPF is a chronic fibrosing interstitial pneumonia of unknown cause. So we have diagnostically excluded any known cause for the disease. So I could make it very short and say the cause is not known.
But of course we have some speculations and we have some evidence also from basic science what might be behind it.
Let’s first talk about increased risks that may show some associations. First there is of course an association with cigarette smoking. So 2/3 of the patients are current or ex-smokers. The odds ratio is below 2.0 to develop IPF if you are a smoker.
Another heavily discussed issue is virus infections. Whether slow virus infections are the cause of IPF and then there is some occupational exposure against wood and metal dust. Also low odds ratio is below 2.0. But the relationship is so low that just as an example it is never recognised as an occupational disorder and re-compensated let’s say if somebody who has worked in a metal industry its IPF he cannot claim that his job has caused this disease.
And other interesting observations have been in the genetic field. So recently we know a little bit more about familial IPF or familial fibrosis. Up to between 5 and 10% of patients have a family history of IPF and in these patients there are some mutations in the surfactant proteins present or mutations in the telomerase genes. Telomerase is an enzyme that is responsible for the telomere shortening and if a cell loses telomeres, finally the cell is not able to divide any more. And there might be the relationship with the aging so that we can say IPF is a premature aging of the lung. So aging processes are associated with it.
And that comes to the last point that really IPF is a disease of the elderly. It’s a sort of geriatric disease. Hardly any patient is younger than 50 years of age, that’s my experience at least in the last 10 years or so when IPF was defined more narrowly. 2/3 of the patients are above 60 and many are already 80 years of age when they are diagnosed.
So aging process may be responsible for the development of IPF.