Biological manifestations of sarcoidosis.

Sarcoidosis is a multisystem granulomatous disease of unknown origin. No si ngle biological marker allows definitive diagnosis of sarcoidosis or may ac curately predict the disease prognosis. However, some biological markers ar e helpful tools as diagnostic aids and disease activity markers. At the blo od level, lymphopenia with CD4 depletion, elevated levels of serum angioten sin converting enzyme, lyzozyme, beta 2 microglobulin and disturbed calcium metabolism resulting in hypercalcemia and hypercalciuria can help guide di agnosis. Lymphocytic alveolitis with a high CD4/CD8 ratio in bronchoalveola r lavage fluid is highly suggestive of the disease. A wide range of new bio logical markers are proposed but their pronostic significance is still cont roversial. In clinical practice, biological markers may help in monitoring treated patients with sarcoidisis.