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Sarcoidosis

Sarcoidosis is a multisystemic, granulomatous disorder that characteristically produces lymphadenopathy, pulmonary infiltration, and skeletal, liver, eye, or skin lesions.

Sarcoidosis occurs most commonly in young adults ages 20 to 40. In the United States, sarcoidosis occurs predominantly among blacks and affects twice as many women as men. Acute sarcoidosis usually resolves within 2 years. Chronic, progressive sarcoidosis, which is uncommon, is associated with pulmonary fibrosis and progressive pulmonary disability.

Causes

The cause of sarcoidosis is unknown, but several possibilities exist. The disease may result from a hypersensitivity response - possibly from T-cell imbalance - to such agents as atypical mycobacteria, fungi, and pine pollen. The incidence is slightly higher within families, suggesting a genetic predisposition. Chemicals also may trigger the disease (zirconium or beryllium lead to illnesses that resemble sarcoidosis).

Although the exact mechanism of the disease is unknown, research suggests a T-cell problem and, more specifically, a lymphokine production problem. In other granulomatous-diseases such as tuberculosis, granuloma formation occurs from inadequate pathogen clearance by macrophages. These macrophages require the help of T cells that secrete Iymphokines, which, in turn, activate less effective macrophages to become aggressive phagocytes. Lack of Iymphokine secretion by T cells may help explain granuloma formation in sarcoidosis.

Signs and Symptoms

Signs and symptoms of sarcoidosis include:

  • A vague feeling of discomfort and fatigue
  • Fever
  • Weight loss
  • Small red bumps on your face, arms or buttocks, a condition more common in blacks than in whites
  • Red, watery eyes
  • Arthritis in your ankles, elbows, wrists and hands, commonly associated with bumps in the skin over your shins (erythema nodosum)

Diagnostic tests

A positive Kveim-Siltzbach skin test points to sarcoidosis. In this test, the patient receives an intradermal injection of an antigen prepared from human sarcoidal spleen or lymph nodes from patients with sarcoidosis. If he has active sarcoidosis, granuloma develops at the injection site in 2 to 6 weeks. When coupled with a skin biopsy at the injection site that shows discrete epithelioid cell granuloma, the test confirms the disease.

Several other tests are used to support the diagnosis: For example, chest X-rays demonstrate bilateral hilar and right paratracheal adenopathy, with or without diffuse interstitial infiltrates. Occasionally, they show large nodular lesions in lung parenchyma. Lymph node, skin, or lung biopsy discloses noncaseating granulomas with negative cultures for mycobacteria and fungi.

Pulmonary function tests indicate decreased total lung capacity and compliance and reduced diffusing capacity, and arterial blood gas (ABG) studies show a decreased partial pressure of arterial oxygen.

Tuberculin skin test, fungal serologies, sputum cultures (for mycobacteria and fungi), and biopsy cultures are negative and help rule out infection.

Treatment

Asymptomatic sarcoidosis requires no treatment. However, sarcoidosis that causes ocular, respiratory, central nervous system, cardiac, or systemic symptoms (such as fever and weight loss) requires treatment with systemic or topical corticosteroids. So does sarcoidosis that produces hypercalcemia or destructive skin lesions. Such therapy usually continues for 1 to 2 years, but some patients may need lifelong therapy. A patient with hypercalcemia also requires a low-calcium diet and protection from direct exposure to sunlight.

If the patient has a significant response to the tubercular skin tests, showing tuberculosis reactivation, he needs isoniazid therapy.

Prevention

Because the cause of sarcoidosis is not known, there is no way to prevent it.



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