Interstitial lung disease

From greek.doctor

Interstitial lung disease (ILD), also called diffuse parenchymal lung disease, is a group of disorders characterised by fibrosis of the lungs. There are many different types. The name implies that these disorders only affect the interstitium of the lung and not the parenchyma (the airways and alveoli), but many of these disorders affect the parenchyma as well.

It's more common in males, but ILD is rare overall.

Etiology

The list of causes of ILD is basically endless, but here are some of the most typical:

  • Idiopathic
    • Idiopathic pulmonary fibrosis
    • Idiopathic interstitial pneumonia
  • Environmental and occupational exposure
    • Silica crystals (causes "silicosis")
    • Asbestos (causes "asbestosis")
    • Coal dust (causes "coal worker pneumoconiosis")
    • Mineral dust
    • Organic dust
  • Drugs
    • 350+ drugs can cause ILD
  • Auto-immune and rheumatological diseases
  • Infiltrative disorders

Most cases of ILD are idiopathic. The most common identifiable causes include exposure- and drug-induced ILD.

Clinical features

Interstitial lung disease causes gradual onset dyspnoea and sometimes cough.

Many ILDs are complicated by pulmonary hypertension, which may be symptomatic.

Diagnosis and evaluation

Pulmonary function testing is obligatory.

ILD has characteristic imaging findings. Radiography usually shows a reticular pattern, a nodular pattern, or a mix of the two. However, high-resolution CT is obligatory in the evaluation. Some types of ILD have characteristic CT findings, but most types show any combination of the following patterns:

  • Ground glass opacities
  • Lung consolidation
  • Reticular opacities
  • Nodules

Idiopathic pulmonary fibrosis has a characteristic sign called honeycombing, named after the honeycomb-like appearance the lung takes on due to formation of clustered cystic air spaces.

Silicosis causes "eggshell calcification", which is well-defined sickle-shaped calcification of the rims of the hilar lymph nodes. Bilateral diffuse ground glass opacities and uniformly distributed small nodules are also typical.

Bronchoalveolar lavage and lung biopsy may be indicated if the type remains uncertain.

Management

In all cases, lifestyle changes which are lung protective are indicated. These include smoking cessation and avoidance of exposures. A corticosteroid or other immunosuppressants may be useful.

In case of ILD secondary to an underlying disorder, it should be treated.