Characteristics of Systemic Lupus Erythematosus
Systemic lupus erythematosus (SLE) is a rheumatic disease that causes many skin lesions around the body and mainly affects women in the childbearing years.
This article contains information you should know about this pathology. Read on to learn about its symptoms and main causes.
What is there to know about systemic lupus erythematosus?
As the scientific literature indicates, systemic lupus erythematosus (SLE) is a rheumatologic disease that affects the skin and connective tissue. It’s the paradigm of autoimmune diseases.
Because it’s an autoimmune disease, its most typical characteristic is the presence of autoantibodies. Therefore, in other words, antibodies produced by the person’s own immune system that “attack” the cells of their own body.
However, in the case of lupus, the final result of these autoantibodies is the appearance of lesions on organs and tissues. This is why it is considered a “systemic disease” or “non-organ specific.” Furthermore, it’s a chronic illness that consists of alternating periods of remission and exacerbation of the symptoms.
Prevalence and etiology
According to data from the MSD Manual, “70 to 90% of cases occur in women (usually of childbearing age). It’s more frequent in Caucasians and Asians and can affect patients of any age, including newborns.”
The exact cause of the disease is unknown. However, it seems undeniable that the etiology is multifactorial.
A number of genetic, hormonal, and environmental factors act on a genetically predisposed immune system. Therefore, this ultimately leads to the typical clinical manifestations of the disease.
A recent study indicates that “ultraviolet radiation is the environmental factor most closely linked to lupus. It exacerbates in 70% of patients by increasing apoptosis of keratinocytes and other cells or by altering DNA and intracellular proteins so they become antigenic.”
The study also states that although the genetic factor is important, it isn’t a sufficient cause for the onset of the disease.
What does it mean for an immune system to be “genetically predisposed”?
A person’s immune system doesn’t trigger an abnormal response just because, but rather because it has a predisposition for it. This predisposition comes from the existence of susceptibility genes.
These genes are indirectly related to the disease and give those who possess them a higher likelihood of experiencing the disease. However, it’s also due to the absence of protective genes.
These factors add up to produce a modified immune response to external or internal factors. Thus, they refer to it as autoimmunity when the response lasts too long.
Determining factors
Genetic factors
Systemic lupus erythematosus has a significant link to HLA – DR3 and HLA – DR2. Moreover, it links to genes that code components of the complement system (relation to deficiency of C2 and C4).
HLA (human leukocyte antigens) are molecules in all cells in a person’s body. Coincidentally, they allow the immune system to differentiate between what is their own (to not attack it) and what is other (to attack it). The complement system comes from molecules with the goal of eliminating anything foreign.
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Hormonal factors
The greater prevalence of systemic lupus erythematosus in women of childbearing age than in men has led to the idea of a link between sex hormones and the illness.
Therefore one’s own hormones (estrogen, progesterone, prolactin, testosterone…) and others (hormone replacement therapy or contraceptives) seem to play an important role in the disease. Meanwhile, there is no consensus on the significance of the influence.
Environmental factors
Some environmental factors seem to trigger or intensify systemic lupus erythematosus.
- UV radiation, associated with photosensitivity (exaggerated response to sunlight). In fact, it is a symptom of the disease and outbreaks after prolonged exposure to the sun.
- Viral infections, such as Epstein-Barr or a retrovirus.
- Medication-induced, where the symptoms could be due to certain medications affecting the immune system. Something that happens with procainamide (antiarrhythmic) or hydralazine (used to treat hypertension).
Pathogeny
The final result is the creation and deposit of immune complexes in tissues of the body. The immune complex is the name given to the molecule resulting from the antigen-antibody union. Moreover, this deposit is one of the main mechanisms by which the tissue lesion is produced, along with the inflammation and apoptosis (cell death) processes that come from the abnormal immune response.
The clinical picture of systemic lupus erythematosus
- General symptoms (95%): fatigue, lack of appetite, weight loss, overall discomfort. Joint pain is almost constant.
- Musculoskeletal manifestations (95%): consist mainly of muscle and joint pain. Coincidentally, these are the most common symptoms.
- Skin lesions (80% of cases): more than half of people with lupus suffer from photosensitivity. In addition, almost half of the patients present lesions in the oral mucosa and nasal cavities in the form of aphthous ulcers. Skin lesions may also appear in any of three ways:
- Acute cutaneous lupus (50%). One of the lesions that are most characteristic of the disease, facial erythema (redness in the face) in the shape of butterfly wings. It doesn’t leave a scar. And its appearance relates to the sun and new outbreaks. It may sometimes be accompanied by a red rash in other areas (neck, shoulders, arms).
- Subacute cutaneous lupus (10%). Symmetric blisters appear on the neck and shoulders with sun exposure. They don’t leave a scar, though they may leave a discoloration of the skin.
- Chronic cutaneous lupus (30%).
- Blood alterations (80%) like chronic anemia.
- Neurological manifestations such as headaches, depression, anxiety, convulsions…
- Lung manifestations in half of the patients. Coincidentally, the most common is pleuritis and the most serious is a massive alveolar hemorrhage (fortunately it is very rare).
- Cardiac manifestations are the most common is pericarditis.
- Lupus nephritis affects half of the patients and is a cause for concern.
- Many other manifestations may be present, depending on the affected organ, such as miscarriage, keratoconjunctivitis, etc.
Diagnosing lupus
In conclusion, the most characteristic symptom of lupus is the appearance of ANA autoantibodies (antinuclear autoantibodies), found in 80-90% of patients.
- ANA isn’t specific to lupus and appears in other autoimmune diseases.
- These antibodies may not be present even if the person has lupus. ANA negative patients (10-20%) may present with Raynaud’s disease.
- Within ANA, Anti DNA DS is the most specific to lupus.
Finally, lupus is a chronic disease that can have asymptomatic periods (referred to as remissions). Thus, it’s important for the patient to follow the instructions of their treating physician and try to maintain a healthy lifestyle.