Sarcoid is a multisystem granulomatous disease with predominant pulmonary manifestations.

While the cause of sarcoid disease is unknown, the underlying pulmonary pathogenesis has been well-delineated. Early sarcoid changes are interstitial. Lymphocytes and histiocytes infiltrate the interstitium in this phase. Microscopic non-caseating granulomas form in the next advanced stage of disease. In some cases these microgranulomas regress; in other cases they coalesce and form macrogranulomatous nodules. The granulomas are found most commonly in the axial interstitium, but also can involve alveolar interstitium and airway mucosa. In a more advanced stage of sarcoid, fibrous tissue deposits in the granulomas' periphery grow inward and replace granulomatous tissue. Lymph node architecture is characteristically replaced in sarcoid in 80% of cases. Commonly lymph node involvement is bilateral and involves the hilar and paratracheal lymph nodes.

Sarcoid can be staged radiographically. These stages parallel the course of the disease and are of prognostic significance. Stage 0 = Normal chest
radiograph, Stage 1 = Bilateral Hilar Lymph Node Enlargement (75% resolve), Stage 2 = Bilateral Hilar Lymph Node Enlargement and Parenchymal Disease, Stage 3 = Parenchymal Disease only (only 10% resolve), Stage 4 = Pulmonary Fibrosis.

Demographics: 20-40 year olds, predominantly African American females.