Sarcoïdose

Sarcoidosis is a multisystemic granulomatous disease of unknown cause, which most frequently involves the lung and the lymphatic system. It is generally observed between 25 and 45 years old. Various clinical phenotypes exist, depending on involved organs, duration and severity. Chest radiography is abnormal in 86-92% of the cases. Four different radiographic stages have been defined, based on the presence or absence of hilar lymphadenopathy and/or lung infiltration with or without fibrosis, each determining a different prognosis. The evolution is favourable in 12-36 months in 50% of patients but the course of the disease can be severe when granulomatous lesions are localized in some particular sites or in case of pulmonary fibrosis. The diagnosis is established on the combination of clinical and radiological presentation, histopathological findings and the exclusion of other granulomatous disorders. Sarcoidosis is characterized by an uncontrolled immunological reaction to unidentified antigens with a low clearance. The formation of the granulomas is controlled by a Th1 type response. The incidence and the clinical phenotype of the disease depend on predisposing genetic factors. Even in the absence of evident cause, several medications including glucocorticoid agents have demonstrated efficacy on granulomatous lesions. Their effect is only suspensive. They are indicated only when a beneficial effect is expected and they must be given for at least one year.