Interstitial lung disease (ILD), also known as diffuse parenchymal lung disease (DPLD),^[1] refers to a group of lung diseases affecting the interstitium of the lung:^[2] alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. The term ILD is used to distinguish these diseases from obstructive airways diseases.

Most types of ILD involve fibrosis, but this is not essential; indeed fibrosis is often a later feature. The phrase "pulmonary fibrosis" is no longer considered a synonym, but the term is still used to denote ILD involving fibrosis.^[3] The term is commonly combined with idiopathic in "idiopathic pulmonary fibrosis",^[4][5][6] denoting fibrotic ILD that cannot be ascribed to a distinct primary cause.

Causes

The alveoli

Micrograph of usual interstitial pneumonia (UIP). UIP is the most common pattern of idiopathic interstitial pneumonia (a type of interstitial lung disease) and usually represents idiopathic pulmonary fibrosis. H&E stain. Autopsy specimen.

1. Inhaled substances
   • Inorganic
     • Silicosis
     • Asbestosis
     • Berylliosis
   • Organic
     • Hypersensitivity pneumonitis
2. Drug induced
   • Antibiotics
   • Chemotherapeutic drugs
   • Antiarrhythmic agents
3. Connective tissue disease
   • Systemic sclerosis
   • Dermatomyositis
   • Systemic lupus erythematosus
   • Rheumatoid arthritis
4. Infection
   • Atypical pneumonia
   • Pneumocystis pneumonia (PCP)
   • Tuberculosis
5. Idiopathic
   • Sarcoidosis
   • Idiopathic pulmonary fibrosis
   • Hamman-Rich syndrome
6. Malignancy
   • Lymphangitic carcinomatosis

Investigation

Patients with pneumocystis pneumonia can present with interstitial lung disease, as seen in the reticular markings on this AP chest x-ray

A lung biopsy is required if the clinical history and imaging is not clearly suggestive of a specific diagnosis or malignancy cannot otherwise be ruled-out.

Treatment

ILD is not a single disease, but encompasses many different pathological processes. Hence treatment is different for each disease.

If a specific occupational exposure cause is found, the person should avoid that environment. If a drug cause is suspected, that drug should be discontinued.

Many idiopathic and connective tissue-based causes of ILD are treated with corticosteroids,^[8] such as prednisolone. Some patients respond to immunosuppressant treatment. Patients with hypoxemia may be given supplemental oxygen.

References

External links

• AIMIP Onlus - Italian Interstitial Lung Diseases No-Profit Organization
• Dorothy P. and Richard P. Simmons Center for Interstitial Lung Diseases at University of Pittsburgh Medical Center
• Interstitial Lung Disease Program at University of Chicago
• PA-IPF - The Pennsylvania Idiopathic Pulmonary Fibrosis State Registry at University of Pittsburgh
• Interstitial Lung Disease Center at University of Cincinnati

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