Family connection in autoimmunity

About 20% of the population have a genetic predisposition to autoimmune diseases.
In my family I have polymyostis, my mother has rheumatoid arthritis, my sister has psoriasis and my father neuropathies and my grandmother had pernicious anemia and hashimoto's thyroidosis.
The good news about the genetic disposition is that not everyone in the family will get a disease as others factors usually trigger the diseases such as long term stress or environmental triggers.