What factors are associated with systemic lupus erythematosus? What are the diagnostic criteria?

Author: Wu Donghai, Chief Physician of China-Japan Friendship Hospital

Reviewer: Zhang Zhuoli, Chief Physician, Peking University First Hospital

Systemic lupus erythematosus (SLE) is an autoimmune disease that affects multiple organs. It is named because the lupus spots on the patient's body resemble scars left after a wolf bite. The most obvious is the butterfly-shaped erythema that appears on the cheeks.

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Systemic lupus erythematosus is more common in women of childbearing age, that is, women aged 20-40, and the male to female incidence ratio is about 1:10.

1. What factors may be related to systemic lupus erythematosus?

The cause of systemic lupus erythematosus is still unclear. Studies have shown that it may be related to genetics, environmental factors, immune disorders, endocrine system, race, etc.

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The incidence of systemic lupus erythematosus varies among different races, with blacks having the highest incidence, followed by yellows, and whites having a relatively low incidence.

Systemic lupus erythematosus has a certain genetic tendency. If parents have systemic lupus erythematosus, the probability of their children suffering from the disease is higher than that of the general population. However, systemic lupus erythematosus is not a genetic disease. It does not mean that children will definitely suffer from the disease if their parents suffer from it. In addition, a study found that if one of the identical twins suffers from systemic lupus erythematosus, the probability of the other suffering from the disease is 50%; if one of the fraternal twins suffers from systemic lupus erythematosus, the probability of the other suffering from the disease is 10%, which also shows that systemic lupus erythematosus is related to genes and heredity.

Now with the development of immunology, it is found that systemic lupus erythematosus is also related to immune disorders. When the body has immune disorders, it will produce autoantibodies to fight against its own tissues or organs, such as its own red blood cells, white blood cells, and kidneys, causing a series of inflammations and injuries.

In addition, there is another theory, which has not yet formed a conclusion and is for reference only. Under normal circumstances, new cells grow and die in the human body every day, and the dead cells are cleared away as quickly as possible. However, in patients with systemic lupus erythematosus, the rate of cell death is accelerated, and the function of clearing dead cells is weakened. Dead cells accumulate in the body, which will also stimulate the immune system and cause immune disorders.

Environmental factors are also thought to play a role in the development of systemic lupus erythematosus. Even in the case of genetic similarity, if one identical twin has the disease, the other has a 50% chance of developing the disease, while if genetics plays a full role, the other should have a 100% chance of developing the disease, indicating that environmental factors may affect the risk of disease. One of the known environmental factors is ultraviolet radiation, which can trigger a series of inflammatory responses in the skin.

Endocrine factors are also thought to be involved in systemic lupus erythematosus, especially given that the disease is more common in women of childbearing age, when estrogen levels are higher, so it is speculated that estrogen may have a certain impact on the occurrence of the disease.

2. Diagnostic criteria for systemic lupus erythematosus

Systemic lupus erythematosus can cause damage to multiple organs such as the kidneys, cardiovascular system, lungs, digestive system, blood system, and eyes. The symptoms are complex and varied, some are joint pain, some are rashes, some are recurrent oral ulcers, and some are kidney involvement. Therefore, patients may go to multiple departments such as dermatology, hematology, and nephrology for treatment, which means that each department should have some knowledge about lupus.

For the diagnosis of systemic lupus erythematosus, the systemic lupus erythematosus classification criteria recommended by the American College of Rheumatology in 1997 are currently generally used. The specific criteria are as follows:

1. Cheek erythema, on the prominent parts of the two cheeks. Fixed erythema, flat or raised;

2. Discoid erythema. It is a flaky erythema that rises from the skin, with keratin scales and hair follicle plugs attached. Old lesions may cause atrophic scars.

3. Photoallergy. A significant reaction to sunlight, causing itching and rash;

4. Oral ulcers. Recurrent oral or nasopharyngeal ulcers, usually painless;

5. Arthritis. Non-erosive arthritis may involve two or more peripheral joints with tenderness and swelling;

6. Serositis. It often manifests as pleurisy or pericarditis;

7. Kidney disease: Urine protein (24h)>0.5g or +++, or casts (red blood cells, hemoglobin, granules or mixed casts);

8. Neurological disease, such as epileptic seizures or psychotic manifestations, excluding drugs or known metabolic disorders;

9. Hematological diseases. Manifested as hemolytic anemia, leukopenia, lymphopenia, or thrombocytopenia;

10. Immunological abnormalities: Positive anti-dsDNA antibodies, positive anti-Sm antibodies or positive anti-phospholipid antibodies, decreased complement;

11. Abnormal antinuclear antibodies. Abnormal antinuclear antibody titers at any time and without the use of drugs to induce "drug-induced lupus".

Patients who meet four or more of the eleven criteria can be diagnosed with systemic lupus erythematosus after excluding infections, tumors and other connective tissue diseases. However, among the four or more criteria that are met, at least one clinical criterion and one laboratory criterion must be present, and there must be both symptoms and serological abnormalities.

Among these eleven classification criteria, immunological abnormalities and high titer antinuclear antibodies are more diagnostically significant. Once immunological abnormalities occur, even if clinical diagnosis is not sufficient, close follow-up should be performed to facilitate early diagnosis and treatment.

The classification criteria for systemic lupus erythematosus proposed by the European/American College of Rheumatology (EULAR/ACR) in 2019 have improved sensitivity and specificity compared with previous standards. They are as follows:

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