This was taken from OMRF - Lupus Genetics study foundation:
The Inheritance of Lupus
Most people who have systemic lupus erythematosus, aka SLE or lupus,
do not have any relatives who also have lupus. Lupus is familial in
only 12-15% of cases. It is clear that lupus varies from one ethnic
group to another.
SLE is thought to be a genetically complex disease, meaning that
several different genes are involved in its development. Scientists
suspect that tens, or even hundreds, of genes may be involved.
According to recent genome-wide genetic scans, these genes may vary
depending on a patient's ethnicity or the disease symptoms from
which the patient suffers. For this reason, it is important for
families of all ethnic backgrounds to participate in lupus research.
While several genomic "hot spots" are currently being explored, some
of the genes have clearly been identified, e.g. FcgammaRIIA ;
FcgammaRIIIA; complement components C2, C4 and C1q; PDCD-1; and
HLA-DR. (A "hot spot" is
an area where scientists believe it is extremely likely lupus genes
exist.)
Many researchers think that lupus is hereditary, meaning it is
passed on genetically from one generation to another. The pattern of
inheritance is, however, unclear. It is known that not everyone who
has the lupus genes develops the disease, as demonstrated in
numerous identical twin studies. The rate at which both
identical twins are affected with lupus varies from
15-69%.
This information indicates, first, that people who have lupus genes
have a genetic predisposition to the disease. Merely having
lupus-linked genes is not enough to cause a person to develop
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lupus. This in turn indicates that an external or environmental
trigger is also involved in lupus disease onset in people with
the genetic predisposition. Known triggers include stress,
hormonal changes, illness, certain viruses including Epstein-Barr
virus and chemical exposure.
Lupus Genes -- How They are Studied
Lupus Geneticists have been conducting familial studies of lupus
for a decade. They study families that are both multiplex and
simplex for lupus. These two kinds of families are useful
in different ways for finding the lupus genes. Multiplex family
research allows for the study of inheritable lupus, or lupus
that is passed on genetically. These studies use DNA samples
(usually blood) from the lupus patients and other unaffected
family members whose relationships may prove useful for genetic
linkage, usually parents, siblings, grandparents, etc. Simplex
family research allows for the study of randomly-occurring
lupus, or cases in which the lupus-associated genes come
together arbitrarily to create a predisposition to disease.
These studiesuse DNA samples (usually blood) from nuclear families, typically
a lupus patient, 1-2 siblings and their parents.
By examining the genes of multiplex lupus families (comparing
the genes of those affected by lupus and the genes of their
unaffected family members) scientists are locating "hot spots"
within the human genome worthy of morespecific study. Multiplex lupus studies have also benefited from
the sub-grouping of families, or grouping families according to
certain
characteristics that they share in common (i.e.-ethnicity, lupus
patients' symptoms, patient gender) to find genes that may be
specific to these groups or symptomologies.
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