Dear Colleagues,

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrosing interstitial lung disease, of unknown etiology, usually affecting adults over 50 years in age, and is associated with a radiological and/or histological pattern of usual interstitial pneumonia. IPF has very limited therapeutic options and an extremely poor prognosis. It is the most frequent diffuse interstitial lung disease. The incidence and prevalence of IPF is not fully understood. Epidemiological studies performed thus far show very variable figures, depending on the criteria used to define the disease, study population, methodology, and study design. However, it is estimated that the incidence is 4.6–7.4 cases/100,000; and the prevalence is 13 cases/100,000 in women, and 20 cases/100,000 in men. It is unknown whether the incidence and prevalence are influenced by ethnic, racial or geographical factors. In recent years, incidence has been reported to be higher, probably due to the improved diagnostic methods and increased life expectancies. The etiology of IPF is unknown, although it is likely that the disease is the consequence of the action of several factors in subjects with genetic predisposition. The relevance of the genetic predisposition is based on the existence of familial forms of the disease. Currently, it has been demonstrated that the disruption of lung tissue and the formation of fibrosis are the result of an abnormal repair of alveolar epithelial lesions, resulting in progressive accumulation of extracellular matrix proteins, decreased fibroblast/myofibroblast balance and death of epithelial cells, without evidence of previous inflammation. Therefore, epithelial cells, fibroblasts and myofibroblasts are considered the main effectors in the progression of the disease. Diagnostic criteria include: (a) exclusion of other causes of interstitial lung disease and (b) presence of the histological pattern of usual interstitial pneumonia in lung biopsy samples or evidence of pattern of usual interstitial pneumonia in high-resolution computed tomography (HRCT) or both. The evolution is variable. The disease can remain asymptomatic for 2–3 years and is sometimes stable for long periods of time. In some cases, the onset of symptoms may occur 6–24 months prior to diagnosis. The most usual evolution is slow progression, although there are accelerated forms, leading to respiratory failure within 6–12 months. The survival is 3–5 years after diagnosis. Patients with IPF can have complications and comorbidities that modify the clinical course and prognosis: pulmonary emphysema, pulmonary hypertension, acute exacerbation, sleep apnea-hipopnea syndrome, gastroesophageal reflux, lung cancer, blood clotting, pneumothorax, and anti-neutrophil cytoplasmic antibodies (ANCA) positive vasculitis. In recent years, two antifibrotic drugs have been included for the treatment of IPF: pirfenidone and nintedanib. Both drugs decrease the progression of the disease and improve its evolution. They are indicated for the treatment of mild-moderate idiopathic pulmonary fibrosis. Non-pharmacological treatments include rehabilitation, lung transplant and home oxygen therapy. Both cell therapy and gene therapy in IPF are undergoing experimental studies. Treatment with stem cells and type II alveolar cells are well tolerated and stabilize the disease. Gene therapy has only been performed experimentally.

In this Special Issue of Medical Sciences, we will cover the recent advances on the diagnosis, pathogenesis, evolution, and treatment of idiopathic pulmonary fibrosis.

Dr. Antoni Xaubet
Guest Editors

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• idiopathic pulmonary fibrosis
• interstitial lung diseases
• cell therapy in idiopathic pulmonary fibrosis