If your sister has Rheumatoid Arthritis is your chance greater?

The exact cause of rheumatoid arthritis (RA) is unclear.
RA is not considered hereditary or inherited.
However, having a family history of RA and certain genes can increase your risk.

Your immune system protects you by attacking foreign substances — like bacteria and viruses — that invade the body. Sometimes the immune system is fooled into attacking healthy parts of your bodies. Researchers have identified some of the genes that control the immune responses. Having these genes increases your risk for RA. However, not everyone who has RA has these genes, and not everyone with these genes has RA.

Some of these genes include:

HLA: The HLA gene site is responsible for distinguishing between your body’s proteins and the proteins of the infecting organism. A person with the HLA genetic marker is five times more likely to develop rheumatoid arthritis than those who do not have this marker. This gene is one of the most significant genetic risk factors for RA.
STAT4: This gene plays a role in regulating and activating the immune system.
TRAF1 and C5: This gene has a part in causing chronic inflammation.
PTPN22: This gene is associated with the onset of RA and the progression of the disease.
Some of the genes thought to be responsible for RA are also involved in other autoimmune diseases, such as type 1 diabetes and multiple sclerosis. This may be why some people develop more than one autoimmune disease.