What is sarcoidosis? Where does it occur?

Author: Fang Baomin, Chief Physician, Beijing Hospital

Reviewer: Zhi Xiuyi, Chief Physician, Xuanwu Hospital, Capital Medical University

Sarcoidosis is a disease that affects all systems of the body. The main pathological manifestation is non-caseous necrotizing epithelioid granuloma, which is actually a granulomatous lesion.

The main site of sarcoidosis is the chest cavity, such as the lungs, hilum, and mediastinal lymph nodes. Other parts can also be affected, but relatively less, such as the eyes, skin, liver, bones, and nervous system.

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The cause of sarcoidosis is still unclear. There is a speculation about the pathogenesis that some kind of exogenous or endogenous antigen stimulates the body's immune system. After the immune cells are activated, they will release a lot of inflammatory mediators, produce immune responses, and finally form granulomatous lesions, leading to sarcoidosis.

The risk factors for sarcoidosis include external factors, such as firefighters and workers producing pesticides or insecticides, who may have a higher incidence of sarcoidosis. There are also some endogenous factors, such as the incidence of sarcoidosis in the population is higher in blacks than in whites and yellows, which shows racial differences.

In terms of the age of onset, it is generally dominated by middle-aged and young people; in terms of gender, there are more females than males; in terms of the region of onset, generally speaking, people in northern my country are more likely to get the disease than people in southern China, and the incidence rate is higher in cold regions than in temperate regions.

The main site of sarcoidosis is the lungs, and the main symptom is cough, which is the most common symptom. If the mediastinal lymph nodes are swollen, the chest may feel a little bloating and pain. Some patients may have a low-grade fever, night sweats, weight loss, etc. These symptoms are non-specific symptoms and can also be caused by other diseases.

It is currently believed that the main cause of death from sarcoidosis is the involvement of the heart and brain. Involvement of other organs, such as the liver, long-term liver disease can cause portal hypertension and lead to upper gastrointestinal bleeding. Therefore, involvement of important organs will cause relatively large harm, while involvement of less important organs, such as the skin, will not cause fatal damage.

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If there are lung symptoms, such as an irritating cough, a chest CT scan is performed first. If sarcoidosis is confirmed or suspected, other tests, including laboratory tests, are performed next to help with the diagnosis. In addition, a bronchial mucosal or lung tissue biopsy can be performed through bronchoscopy. If non-caseous necrotizing epithelioid granulomas are found in pathological examination, a clear diagnosis can be made. Pathological diagnosis is the gold standard for confirming sarcoidosis.

Sarcoidosis is generally a disease with a relatively good prognosis. Literature reports that 60% of patients can recover without treatment.

The first choice for treating sarcoidosis is glucocorticoids, followed by immunosuppressants. Because sarcoidosis is mainly caused by the activation and proliferation of T lymphocytes and the hyperactivity of the local immune system, glucocorticoids and immunosuppressants are needed to suppress the immune response.

For patients with sarcoidosis, glucocorticoids are used selectively, mainly based on the degree of functional impairment. If the functional impairment is not very severe, it can generally be observed. When the functional impairment is more severe or the symptoms are more severe, such as coughing, chest tightness, and dyspnea, glucocorticoids are considered in this case.

Seventy to eighty percent of patients can be cured through glucocorticoids. Those who eventually develop diseases such as interstitial lung disease and pulmonary fibrosis account for about 10 percent of all sarcoidosis. Most cases of sarcoidosis can be cured.

If patients with sarcoidosis have contraindications to glucocorticoids, other drugs can be considered. For example, for cutaneous sarcoidosis, hydroxychloroquine can be used for treatment, and other parts can consider the use of immunosuppressants, such as methotrexate or methotrexate combined with hydroxychloroquine.

Sarcoidosis is prone to relapse. In order to prevent relapse, the treatment time is generally relatively long. At present, it is generally recognized that the treatment time is at least one year, and some may be longer, such as one and a half to two years. Even in this case, some patients relapse during the process of reducing hormones or after stopping hormones. After relapse, they have to start treatment from the beginning, which may take longer.