Pulmonary Sarcoidosis

Sarcoidosis is a multisystem inflammatory disease in which nonnecrotizing granulomas form in affected tissue. The lungs and intrathoracic lymph nodes are involved most often. A granuloma is an organized cluster of immune cells attempting to contain a perceived threat; in sarcoidosis, the trigger remains unknown. Granulomas may resolve with little residual injury. Persistent inflammation, however, can narrow airways, impair gas transfer, and eventually remodel the lung into fibrosis. This explains why two patients with similar chest imaging can have very different illness: one may have stable hilar lymph-node enlargement and no functional limitation, while another has falling lung volumes, exertional hypoxemia, and progressive scarring. “Noncaseating” does not mean “automatically sarcoidosis.” It describes granulomas without the central necrosis classically associated with tuberculosis. Tuberculosis, fungal infection, chronic beryllium disease, malignancy-related granulomatous reactions, and other inflammatory disorders must still be considered before immunosuppression is prescribed.