Interstitial Lung Diseases

• A large group of diseases with different causes but with the same or similar clinical and pathological changes.
• The interstitial lung diseases (ILD) are diseases of lung parenchyma/ alveoli/ alveolar epithelium/ capillary endothelium/ and the spaces between These structures/ perivascular and Imphatic tissues.
• These are due to chronic, nonmalignant, noninfectious diseases of the lower respiratory tract characterized by inflammation and disruption of the walls of the alveoli.
• Diffuse parenchymal lung diseases, often collectively referred to as the interstitial lung diseases (ILDs), are a heterogeneous group of disorders that are classified together because of similar clinical, roentgenographic, physiologic, or pathologic manifestations (show table ) .
• This manifests clinically as a limitation in the ability of the lungs to transfer oxygen from the alveoli to the pulmonary capillary bed.
• However, the term interstitial is misleading, since most of these disorders are also associated with extensive alteration of alveolar and airway architecture.
• Patients with these disorders are dyspneic first in connection with exercise and, later, as the disease progresses, even at rest.
• There is diffuse parenchymal lung involvement, con­nective tissue involvement, and either fibrosis or granuloma formation. The cause may be known or unknown.
•  The disease may have 2 phases – Acute & Chronic phase. The disease is usually recurrent.
• Interstitiai C1iseases of unknown etiology Sarcoidosis,’Idiopathic pulmonary fibrosis, Wegener’s granulomatosis, SLE, rheumatoid arthritis, tioodpasture’s syndrome.
• Interstitial diseases of known etiology Asbestos, drugs like amiodarone, antibiotic, gold, hypersensitivit neumonitis.

Clinical Features of Interstitial Lung Diseases

• Presentation may be acute, sub-acute or chronic. Age commonly affected is 20 – 40 years.
• There may be a family history of interstitial lung dis­ease.
• Some diseases are more common in women but pneu­moconfosis is mOre common in men.
• ILD is very common in smokers.
• Symptoms are dyspnoea, wheezing, substernal dis­comfort, chest pain, hemoptysis, fatigue, weight loss .

Interstitial Lung Diseases  Physical examination

• Tachypnoea, bilateral basal inspiratory crackles, Wheeze, cyanosis, and clubbing.

Lab diagnosis

• ANA (Antinuclear antibodes), anti immuno globulin antibodies, circulating immune complexes, anti-base­ment anti~6dies=-serum _Rr~ciRitins in hypersensitivity pneumonitis.

X-RAY

• Bilateral basal reticular pattern.
• Nodular opacities especially in upper zones. -)Honey-combing.
• Progressive changes of fibrosis.

CT – HRCT

• CT and High resolution CT for early detection and con­firmation.

Pulmonary function test

• Spirometry and lung volumes show a restrictive de­fect with reduced total lung capacity, reduced FEV₁ and FVC, increased FEV₁ j FVC.

Diffusing capacity

• There is reduction in diffusing capacity for carbon monoxide in ILDs.

Arterial blood gases

• May be normal, or show hypoxaemia, respiratory al­kalosis, hypocapnia, normocapnia, and rarely hyper­capnia.

Fiberoptic bronchoscopy and bronchoalveolar la­vage

• Is useful for diagnosis of sarcoidosis, hypersensitiv­ity pneumonitis.

Treatment of Interstitial Lung Diseases

•   Removal of stimulus
• Suppression of inflammation
• Supplemental oxygen
•  Glucocorticoids-Prednisone 1 mg/kg once daily’ orally for 4-12 wks.
•   Cyclophosphamide and Azathioprine 0,/ Lung transplantation.