Investigators have already discovered that 2 to 3 percent of people who have a close relative with rheumatoid arthritis&mdashi.e. a parent, sibling or child&mdashwill eventually be diagnosed with the disease too.
Much of the research on families has been conducted by the North American Rheumatoid Arthritis Consortium. The consortium comprises researchers from 12 medical centers across the country. They have been carefully analyzing clinical findings and genetic material from 1,000 pairs of siblings who both have rheumatoid arthritis. By testing 400 different genetic regions, the researchers hope they can identify the specific genes associated with the disease. They also hope to pinpoint other genes involved in the spondyloarthropathies, an umbrella term for the class of arthritic conditions that affect the spine and other joints, as well as other rheumatic diseases.
So far, their research has confirmed an association between the development of rheumatoid arthritis and a cluster of genes involved in immune function called the human leukocyte antigen (HLA) complex.
HLAs refer to markers that influence the function of the body's immune system. The immune system uses the HLAs to differentiate self cells and non-self cells. A self cell is any cell that displays that person's HLA type and belongs to that person&mdashand therefore is not an invader. A cell that displays some other HLA type is non-self and is classified as an invader. HLA types are inherited. Some are thought to be connected to autoimmune disorders and other diseases.
