Lupus does not have a "cause", but is probably explained by several "causes", which are combined like pieces of a puzzle.

These “pieces” are specific to each individual (immunogenetic factors) and also come from our environment (environmental factors).

The genetic origins of lupus

Systemic lupus is not an inherited disease, but genetic factors come into play. Each taken in isolation is not enough to cause lupus, except in very rare forms. Thus, systemic lupus very rarely occurs in a familial form. These genetic peculiarities are not, with some exceptions, a major abnormality of a single gene (as in a genetic disease such as hemophilia), but rather "genetic originalities".

These "originalities" seem to be related to small differences (called polymorphisms) that characterize certain immunity genes.

When they add up (hence the term "multigenic disease"), they promote the appearance of disturbances in the immune system.

The environmental origins of lupus

The environmental factors that can trigger lupus are also quite numerous, but none can trigger the disease on its own. It certainly takes several environmental factors (associated with the genetic disruption of the immune system) to cause the disease.

The most likely environmental factors are viruses, such as those of infectious mononucleosis (Epstein-Barr virus), and different drugs, as well as, probably, some toxic factors (much less known).

Other important factors, such as UV light (from the sun) and certain female hormones (oestrogen) also come into play. Tobacco also increases the risk of developing lupus.

Lupus is thus a disease that is described as multifactorial, because it is related to the addition of multiple predisposing, immunogenetic and environmental factors. This multifactorial origin explains why there are lupus of different severity, some of which can begin in children, others in "senior" adults.