Sarcoidosis
In sarcoidosis, clinical staging is based on the chest radiograph:
- Stage 0: Normal chest radiograph
- Stage I: Hilar and mediastinal lymph node enlargement
- Stage II: Lymphadenopathy and parenchymal disease
- Stage III: Parenchymal disease only
- Stage IV: Pulmonary fibrosis
Intrathoracic lymphadenopathy is the most common finding in sarcoidosis occurring in over 85% of patients. The most common pattern is right paratracheal and bilateral hilar adenopathy (the \"1,2,3 sign\"). Unusual patterns of lymph node enlargement occasionally occur. While not common, paratracheal, subcarinal, aortopulmonary window, and other mediastinal lymph node groups can be involved in the absence of hilar disease.
The radiographic appearance of parenchymal disease can be fine nodular, reticulonodular, acinar and very rarely focal (solitary nodule or mass). Acinar opacities in sarcoidosis may coalesce to give the appearance of the so-called alveolar form of sarcoidosis