To briefly review the pathophysiology and clinical features ofsarcoidosis. To describetypical and atypicalhigh-resolution CTfindings. Tohighlight useful findings in differential diagnosis with other entities.

Sarcoidosis is a multisystem chronic inflammatory condition of unknown etiology, characterized by the presence of non-caseous epithelioid cell granulomas and changes in tissue architecture, which may affect almost any organ. Pulmonary manifestations are present in ~ 90% of cases and account for most of the morbidity and mortality associated with the condition. The clinical picture may include respiratory symptoms such as cough and dyspnoea, or nonspecific complaints as fatigue, night sweats, and weight loss. In up to 50% of cases, the patient is asymptomatic, with...

Radiographic Findings Chest radiography is usually the first imaging method, with 60-70% of patients having pathologic findings. More than five decades ago, Siltzbach developed a radiographic system that encompasses 5 stages, according to the pattern of the findings Fig. 1 . It defines the following five stages of sarcoidosis: stage 0, with a normal appearance; stage I with bilateral hilar lymphadenopathy; stage II with hilar lymphadenopathy with pulmonary infiltrates; stage III with parenchymal infiltrates; and stage IV with irreversible fibrosis with parenchymal distortion or bullae....

Sarcoidosis has a wide spectrum of thoracic manifestations. In most patients, pulmonary abnormalities are seen at some stage, with the most common being enlarged hilar and paratracheal lymph nodes, with or without simultaneous parenchymal changes. HRCT is an important tool in the presumptive diagnosis of sarcoidosis, and is superior to radiography, improving the detection of subtle parenchymal abnormalities. It is also important as a prognostic tool, allowing differentiation of reversible from an irreversible disease.

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