Abstract
Sarcoidosis is a multisystemic disorder of unknown etiology. Formation of non-caseating epithelioid cell granulomas in the involved organs is the main feature. Sarcoidal granulomas may involve any organ, but generally clinical sarcoidosis manifests intrathoracic lymph node enlargement, pulmonary involvement, skin or ocular signs and symptoms, or some combination of these findings. Epidemiologically, sarcoidosis affects people of all racial and ethnic groups, although the incidence of sarcoidosis varies widely throughout the world and is most common in women and in people of Scandinavian or African-American descent. Sarcoidosis may occur at any age, but is usually seen in adults under the age of 50 (Dempsey et al., 2009; Iannuzzi et al., 2007; Fernandez-Faith & McDonnell, 2007). Sarcoidosis has long been characterized by many unknown variables: antigen, genetic susceptibility, and factors influencing severity (Noor & Knox, 2007). Clinically, non-specific systemic symptoms such as fatigue, night sweats, and weight loss are common in sarcoidosis patients. Tuberculin skin test is classically negative in patients with sarcoidosis, since activated T-lymphocytes are sequestered at the site of sarcoidal granulomas, leading to peripheral depletion (Dempsey et al, 2009). However, a negative result of the tuberculin test is not specific to sarcoidosis. The Kveim-Siltzbach test, in which cutaneous injection of homogenate of human sarcoid tissue extract and subsequent biopsy are performed, is currently less often used because of many constraints and lower sensitivity. Sarcoidal granulomas produce angiotensin I-converting enzyme (ACE), whose levels are elevated in 60% of patients with sarcoidosis, but the importance of using serum ACE levels in diagnosing sarcoidosis remains controversial (Iannuzzi et al., 2007). Currently, the diagnosis of sarcoidosis is based on three different features: (1) a typical clinico-radiological presentation, (2) the histological evidence of non-caseating granuloma, and (3) exclusion of other possible diseases causing granuloma (Ma et al., 2007). The typical clinico-radiological presentation includes the presence of bilateral hilar adenopathy in chest radiograph of an asymptomatic patient, Lofgren syndrome (combination of erythema nodosum, bilateral hilar adenopathy in chest radiograph, and arthritis), and a gallium-67 uptake in the parotid and lacrimal glands (Panda sign) as well as in the right paratracheal and bilateral hilar (Lambda sign). Diagnostic criteria of sarcoidosis have been thus
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