Definition

Idiopathic interstitial fibrosis is a disease characterized by diffuse interstitial fibrosis of unknown etiology and frequently occurs between the ages of 50-70.

Clinical Picture

• Patients present with dry cough and shortness of breath.
• Clubbing, tachypnea and persistent coarse basal crackles are encountered on physical exam. Often they are using accessory muscles of inspiration for tidal breathing.
• Chest x-ray shows interstitial thickening, honeycombing and nodules in various combination. In Desquamative interstitial pneumonitis alveolar features can be recognized..
• PFT shows a restrictive and diffusion defects. Patients are hypoxic and desaturate significantly with exercise.

Pathology

• The pathology, which is non-specific, varies with the stage of the disease.
• The dominant pattern is inflammatory early on leading to organization of the exudate and interstitial fibrosis in the later stage.
• The severe septal thickening (fibrosis) leads to a "honeycomb" appearance of the lung and pronounced alveolocapillary block.
• Desquamative Interstitial pneumonitis (DIP), Usual Interstitial Pneumonitis (UIP), Lymphocytic Interstitial Pneumonitis( LIP) are various subgroups, probably of the same disease process.

Etiology/Pathogenesis
Unknown. This pathologic condition may be the end stage of many different pulmonary diseases.

Pathophysiology

• Hypoxemia, dyspnea, cyanosis, pulmonary hypertension and cor pulmonale.
• Lungs become stiff and smaller leading to restrictive defect in PFT.
• There is barrier for gas transfer resulting in increased diffusion capacity.
• V/Q mismatch and diffusion barrier leads to widened A-a gradient.

Diagnosis

• Transbronchial lung biopsy confirms pathologically interstitial fibrosis.
• It will be necessary to rule out other known causes for fibrosis like Silicosis or drugs. A long list of conditions can give rise to interstitial fibrosis.

Treatment

• Steroids is useful in acute stages when there is significant inflammatory process.
• Once the fibrosis is chronic or if the chest X-ray has been stable for years or if there is honeycombing, therapy is of no benefit.
• In some cases Methotrexate, Plasmapheresis and Lung Transplant are considerations.
• Oxygen is often prescribed for these patients, probably not influencing pulmonary hypertension.

Prognosis

• In the acute progressive form "Hamman-Rich Syndrome" the prognosis is poor.
• In the chronic form patients can live long with disability.