Thin-walled ring shadows in early pulmonary sarcoidosis.

The appearance of ring shadows on the chest radiograph of patients with sarcoidosis is usually associated with generalised, irreversible pulmonary fibrosis. We report three patients in whom thin-walled ring shadows appeared early in the disease. These ring shadows occurred in areas of pre-existing lung shadowing and in two patients they disappeared with corticosteroid therapy over a period of 1-2 years. We postulate that these early sarcoid ring shadows may be caused by a combination of central necrosis of areas of coalescent granulomas and a check-valve mechanism beyond partial obstruction of airways by endobronchial sarcoidosis.