Course and prognosis of sarcoidosis
The prognosis for sarcoidosis is relatively good overall, but depends strongly on the stage of the disease in which the patient is diagnosed.In stage 1, in acute cases, 90% of patients experience spontaneous healing, and even in stage 2 there is still a relatively high rate of spontaneous healing. In stage 3, however, the use of glucocorticoids such as cortisone is recommended for therapy, often requiring a very long hospital stay. In any case, the course of the disease must be monitored very closely. Suitable control parameters include a lung function test and blood tests. The mortality rate caused by sarcoidosis and its consequences is estimated to be about 5%.
Causes of Sarcoidosis
Many attempts have been made to clarify the cause of sarcoidosis, so far unfortunately in vain. Due to a high incidence of sarcoidosis in families and in identical twins, it has been assumed for some time that it is a genetic defect. In 2005, a specific gene (the BTNL2 gene) was discovered, which increases the risk of developing sarcoidosis by at least 60% when mutated, i.e. altered.
The gene is located on chromosome 6, and at the center of the disease (sarcoidosis) is an abnormal and excessive immune response (immune system) of the body to a specific substance, a specific antigen, which is still unknown. Some bacteria, viruses and organic substances have already been mentioned as triggers. If such a substance enters the body, the organism in some people reacts excessively and tries to protect itself against the substance. This happens with the help of granuloma formation, i.e. nodular formation, in which a kind of protective wall is built up around the substance from various cells so that it cannot spread further. Very specific cell types are involved in the formation of these granulomas, so-called epitheloid cells and also lymphocytes (sarcoidosis).
Diagnosis of Sarcoidosis
In addition to the physical examination, various imaging procedures and laboratory tests are available for the diagnosis of sarcoidosis. An X-ray of the ribcage is taken as standard. The other diagnostic methods are described in more detail below for the particularly interested reader: A pulmonary lavage (BAL, bronchoalveolar lavage) is performed to cytologically examine the secretion obtained.
In sarcoidosis, lymphocytic alveolitis (inflammation of the pulmonary alveoli with increased levels of lymphocytes) with an increased CD4/CD8 ratio is observed: This means that although there are more T-cells (immune cells), their function is disturbed. It is also possible to take a biopsy of lymph nodes of the lung or a biopsy of lung tissue during a lung endoscopy. The histological examination of the tissue shows non-caustic epithelioid cell granulomas (connective tissue nodules) with giant Langhans cells and a border wall of lymphocytes, monocytes and connective tissue cells.
Blood tests for sarcoidosis show elevated inflammation levels and an increased blood sedimentation rate (BSG). In addition, the values for antibodies and immunoglobulin G are elevated. In the case of kidney involvement, calcium and calcitriol are elevated.
Further tests include creatinine, urea and a urine test to assess kidney function. Lung function is examined by spirometry. ACE (angiotensin converting enzymes) and S-IL-2R (soluble IL-2 receptor) are activity markers for lung diseases, they decrease with successful therapy of sarcoidosis. Further examinations in sarcoidosis include an ECG to rule out arrhythmia of the heart, a visit to the ophthalmologist (eye involvement?) and a tuberculin test (which is negative because of the disturbed T-cell function).
