Idiopathic Pulmonary Fibrosis (IPF), also known as Cryptogenic fibrosing alveolitis, is a chronic progressive interstitial lung disease of unknown etiology.

More specifically, IPF is defined as a distinctive type of chronic fibrosing interstitial pneumonia of unknown cause associated with a histological pattern of UIP.

Pulmonary fibrosis has often been called an autoimmune disease. However, it is perhaps better characterized as an abnormal and excessive deposition of fibrotic tissue in the pulmonary interstitium with minimal associated inflammation. Autoantibodies, a hallmark of autoimmune diseases, are found in a minority of patients with truly idiopathic pulmonary fibrosis. Moreover, many autoimmune diseases associated with \"pulmonary fibrosis\", such as scleroderma, are more frequently associated with a related but more inflammatory disease, nonspecific interstitial pneumonitis.

Idiopathic pulmonary fibrosis is a type of idiopathic interstitial pneumonia (IIP), which in turn is a type (or group) of interstitial lung diseases. [5]

Idiopathic interstitial pneumonias include:

Idiopathic Pulmonary Fibrosis is slightly more common in males and usually presents in patients greater than 50 years of age. Average survival from time of diagnosis varies between 2.5 and 3.5 years.

Symptoms are gradual in onset. The most common are dyspnea, but also include nonproductive cough, clubbing, and crackles. It should be noted that these features are non-specific and can occur in a spectrum of other pulmonary disorders.

. It has long been recognized that patients with interstitial lung disease related to asbestos exposure, drugs (particularly chemotherapeutic agents), a connective tissue disease, or other diseases may have features that are difficult to distinguish from IPF. Important differential diagnostic considerations include asbestosis; interstitial lung disease related to scleroderma, mixed connective tissue disease, or rheumatoid arthritis; advanced sarcoidosis, hypersensitivity pneumonitis, or Langerhans\' cell histiocytosis; chronic aspiration; radiation-induced fibrosis; as well as previous therapy with cyclophosphamide, nitrofurantoin, methotrexate, and other drugs

Plain chest x-rays reveal decreased lung volumes, typically with prominent reticular interstitial markings near the lung bases and posteriorly. Honeycombing, a pattern of dense fibrosis characterized by multiple tiny air-filled spaces located at the bases of the lungs, is frequently seen in advanced cases. In less severe cases, these changes may not be evident on a plain chest film.

High-resolution CT scans of the chest demonstrate a symmetrical pattern of bibasilar, peripheral, and subpleural intralobular septal thickening, fibrotic changes, honeycombing, and traction bronchiectasis and bronchiolectasis. There may be associated ground glass opacity of the lungs but these changes are relatively minor in comparison with the fibrotic changes.

Spirometry classically reveals a reduction in the vital capacity with either a proportionate reduction in airflows, or increased airflows for the observed vital capacity. The latter finding reflects the increased lung stiffness (reduced lung compliance) associated with pulmonary fibrosis, which leads to increased lung elastic recoil.

Measurement of static lung volumes using body plethysmography or other techniques typically reveals reduced lung volumes (restriction). This reflects the difficulty encountered in inflating the fibrotic lungs.

The diagnosis of IPF can be made by demonstrating UIP pattern on lung biopsy in a patient without a clinical features suggesting an alternate diagnosis . Establishing the diagnosis of IPF without a lung biopsy has been shown to be reliable when expert clinicians and radiologists concur that the presenting features are typical of IPF.

MAJOR CRITERIA (all 4 required):

MINOR CRITERIA (3 of 4 required):

 There is currently no consensus on the treatment of IPF.

Small early studies demonstrated that the combination of prednisone with either cyclophosphamide or azathioprine over many months had very modest, if any, beneficial effect in IPF, and were associated with substantial adverse effects (predominantly myelotoxicity). Other treatments studied have included interferon gamma-1b and the antifibrotic agent pirfenidone. While neither drug has been shown to have substantial benefits over time, both are currently being studied in patients with IPF. Finally, the addition of the antioxidant N-acetylcysteine to prednisone and azathioprine produced a slight benefit in terms of FVC and DLCO over 12 months of follow up. However, the major benefit appeared to be prevention of the myelotoxicity associated with azathioprine.