Causes

Systemic lupus erythematosus (SLE) is an autoimmune condition, which means it's caused by problems with the immune system.

The immune system is the body's natural defence against illness and infection. When the immune system detects the presence of an infectious agent, such as bacteria or a virus, it sends white blood cells and antibodies to attack it.

In cases of SLE, antibodies released by the immune system can attack healthy tissue, cells and organs.

It's not clear exactly why this happens, although most experts think SLE has more than one cause.

It's been suggested there may be a number of genetic factors that make people more susceptible to the condition, and that it also takes one or more environmental factors to trigger SLE in those who are susceptible.

Genetic factors

Brothers and sisters of people with SLE are much more likely to develop the condition than the population at large.

Researchers have identified a number of different genetic mutations that seem to make people more susceptible to developing SLE. A genetic mutationis a permanent alteration in the DNA sequence that makes up a gene.The DNA in a gene spells out specific instructions for making a protein,so when these instructions are altered, the body's processes do not work normally.

Most faulty genes are associated with regulating certain functions of the immune system, which may explain why the immune system in people with SLE starts to malfunction.

Environmental factors

A number of environmental factors may be responsible for triggering SLE in vulnerable individuals, although the evidence for many of these is limited.

Possible environmental factors that have been suggested include:

• exposure to sunlight (ultraviolet light)
• hormonal changes that occur during a woman's lifetime, such as duringpuberty or pregnancy
• certain infections, such as by theEpstein-Barr virus (EBV)a common viral infection that doesn't usually cause any symptoms
• smoking