What is Systemic Lupus Erythematosus?

Systemic lupus erythematosus is the quintessential autoimmune disease. Learn more about it in this article.

Systemic lupus erythematosus (SLE) is a rheumatic disease (a disease that affects the skin and connective tissues), considered the quintessential autoimmune disease.

Because it’s an autoimmune disease, its most typical characteristic is the presence of autoantibodies. In other words, antibodies produced by the person’s own immune system that “attack” the cells of their own body.

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.”

It’s a chronic illness that consists of alternating periods of remission and exacerbation of the symptoms.

Prevalence

Systemic lupus erythematosus affects females more often (10:1) as well as blacks (3:1). The risk is greater for direct relatives of people with the disease than in the rest of the population.

Up to 65% of cases appear when the person is between 20 and 40 years old.

Etiology

The exact cause of the illness is unknown though it does seem undeniable that it is multifaceted.

A series of genetic, hormonal, and environmental factors act on a predisposed immune system, ultimately leading to the typical clinical presentation 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 (genes indirectly related to the disease that make those who possess them have a higher likelihood of suffering from the disease) and the absence of protective genes.


These factors add up to a modified immune response to external or internal factors. 

When the response is too prolonged, they call it autoimmunity.

Determining factors

Genetic factors

Systemic lupus erythematosus has a significant link to the HLA – DR3 and the HLA – DR2 and genes that code components of the complement system (relation with deficiency of C2 and C4).

The HLA (human leukocyte antigens) are molecules in all cells in a person’s body. 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 that others.

Hormonal factors

The greater prevalence of systemic lupus erythematosus in women of child-bearing 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, while there is no consensus on the significance of the influence.

Environmental factors

Some environmental factors seem to have the ability to trigger or intensify systemic lupus erythematosus.

  • UV radiation, associated with the photosensitivity (exaggerated response to sunlight) that is 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. (Immune complex is the name given to the molecule resulting from the antigen – antibody union.)

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.

Systemic lupus erythematosus

General symptoms (95%): fatigue, lack of appetite, weight loss, overall not feeling well. Joint pain is almost constant.

Musculoskeletal manifestations (95%): consists mainly of muscle and joint pain. These are the most common symptoms.

Skin lesions (80% of cases): more than half of people with lupus present with photosensitivity. Skin lesions may present in any of three ways:

  1. Acute cutaneous lupus (50%): one of the lesions that is 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…).
  2. Subacute cutaneous lupus (10%): symmetric blisters appear on the neck and shoulders with sun exposure. They don’t leave a scar, though may leave a discoloration of the skin.
  3. Chronic cutaneous lupus (30%): Almost half of patients present with ulcer-like lesions in the mucous membrane of the mouth and nasal cavities.

Blood alterations (80%): the most common is chronic anemia.

Neurological manifestations: such as headaches, depression, anxiety, convulsions…

Lung manifestations: in half of patients. The most common is pleuritis and the most serious is a massive alveolar hemorrhage (fortunately it is very rare).

Cardiac manifestations: the most common is pericarditis.

Lupus nephritis. It affects half of patients and is a bad sign.

Many other manifestations may present, depending on the affected organ, such as miscarriage, keratoconjunctivitis…

Diagnosing lupus

So, the most characteristic symptom of lupus is the appearance of ANA autoantibodies (antinuclear autoantibodies), found in 80-90% of patients.

  • ANA are not specific to lupus, as they are seen 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 are the most specific to lupus.
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