Sarcoidosis is a multisystem, granulomatous disease of unknown etiology. It may involve almost any organ or tissue but most commonly involves the lungs, lymph nodes, liver, spleen, central nervous system, skin, eyes, fingers, and parotid glands. The dis-ease is not gender-specific, but some manifestations are more common in women. In the United States, the disease is 10 times more common in African Americans (40 cases per 100,000) than in Caucasians (5 cases per 100,000), and the disease usually be-gins in the third or fourth decade of life (American Thoracic Society, 1999).
Sarcoidosis is thought to be a hypersensitivity response to one or more agents (bacteria, fungi, virus, chemicals) in people with an in-herited or acquired predisposition to the disorder. The hypersensi-tivity response results in granuloma formation due to the release of cytokines and other substances that promote replication of fibro-blasts. In the lung, granuloma infiltration and fibrosis may occur, resulting in low lung compliance, impaired diffusing capacity, and reduced lung volumes (American Thoracic Society, 1999).
A hallmark of this disease is its insidious onset and lack of promi-nent clinical signs or symptoms. The clinical picture depends on the systems involved. With pulmonary involvement, signs and symptoms may include dyspnea, cough, hemoptysis, and con-gestion. Generalized symptoms include anorexia, fatigue, and weight loss. Other signs include uveitis, joint pain, fever, and granulomatous lesions of the skin, liver, spleen, kidney, and cen-tral nervous system. The granulomas may disappear or gradually convert to fibrous tissue. With multisystem involvement, the pa-tient has fatigue, fever, anorexia, weight loss, and joint pain.
Chest x-rays and CT scans are used to assess pulmonary adenopa-thy. The chest x-ray may show hilar adenopathy and disseminated miliary and nodular lesions in the lungs. A mediastinoscopy or transbronchial biopsy (in which a tissue specimen is obtainedthrough the bronchial wall) may be used to confirm the diagno-sis. In rare cases, an open lung biopsy is performed. Diagnosis is confirmed by a biopsy that shows noncaseating granulomas. Pul-monary function test results are abnormal if there is restriction of lung function (reduction in total lung capacity). Arterial blood gas measurements may be normal or may show reduced oxygen levels (hypoxemia) and increased carbon dioxide levels (hypercapnia).
Many patients undergo remission without specific treatment. Corticosteroid therapy may benefit some patients because of its anti-inflammatory effect, which relieves symptoms and improves organ function. It is useful for patients with ocular and myocar-dial involvement, skin involvement, extensive pulmonary disease that compromises pulmonary function, hepatic involvement, and hypercalcemia. Other cytotoxic and immunosuppressive agents have been used, but without the benefit of controlled clinical tri-als. There is no single test that monitors the progression or re-currence of sarcoidosis. Multiple tests are used to monitor the involved systems.