Interstitial Lung Diseases of Unknown Cause: Disorders Characterized by Chronic Inflammation of the Lower Respiratory Tract

Sarcoidosis Sarcoidosis is a multisystem granulomatous disease of unknown cause characterized by enhanced cellular immune processes at sites of involvement.^36,53,59,152 Almost all organs can be affected by the disease, but the lower respiratory tract is the site most commonly associated with morbidity and mortality.¹⁵² At least 90 per cent of patients with sarcoidosis have pulmonary manifestations; 20 to 25 per cent of these patients have a permanent loss of lung function, and 5 to 10 per cent die from complications of the disease.^153,154 Sarcoidosis is found throughout the world.^{152 153 154 155} In the industrialized nations, the prevalence varies by sex, geographic location.