Sarcoidosis is an uncommon systemic granulomatous disease of unknown cause that affects skin, lungs, lymph nodes, liver, spleen, parotid glands, and eyes. Less commonly involved organs indicative of more severe disease are the central nervous system, heart, bones, and upper respiratory tract. Any one of these organs or all of them may be involved with sarcoid granulomas. Lymphadenopathy is the single most common finding. African-Americans are affected more often than Caucasians. Only the skin manifestations of sarcoidosis are discussed here.
PRIMARY LESIONS. The superficial lesions consist of reddish papules, nodules, and plaques, which may be multiple or solitary and of varying size and configuration. Annular forms of skin sarcoidosis are common. These superficial lesions usually involve the face, the shoulders, and the arms. Infiltration of sarcoidal lesions frequently occurs at scar sites. Subcutaneous nodular forms and telangiectatic, ulcerative, erythrodermic, and ichthyosiform types are rare. Lupus pernio is most often seen in African-American females. It is often associated with chronic systemic disease.
SECONDARY LESIONS. Central healing can result in atrophy and scarring.
COURSE. Most cases of sarcoidosis run a chronic but benign course with remissions and exacerbations. Spontaneous "cure" is not unusual.
Erythema nodosum is characteristic of acute benign sarcoidosis (see Chap.12). Lupus pernio (indurated violaceous lesions on ears, nose, lips, cheeks, and forehead) and plaques are characteristic of chronic, severe, systemic disease.
ETIOLOGY. The exact cause is unknown, but the clinicopathologic picture undoubtedly can be caused by several agents, including bacteria, fungi, and certain inorganic agents.
LABORATORY FINDINGS. The histopathology is quite characteristic and consists of epithelioid cells surrounded by Langhans' giant cells, CD4 lymphocytes, some CD8 lymphocytes, and mature macrophages. No acid-fast bacilli are found, and caseation necrosis is absent. The Kveim test, using sarcoidal lymph node tissue, is positive after several weeks. Tuberculin-type skin tests are negative (anergic). The total blood serum protein is high and ranges from 7.5 to 10.0 grams/dL, mainly because of an increase in the globulin fraction.
Angiotensin-converting enzyme (ACE) deficiency may be noted.
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