Genetics and arthritis

Is Arthritis All In The Family?
Why Me? Is It In The Genes?
Why does one person get arthritis as opposed to another person?
Why is a person afflicted with rheumatoid arthritis rather than osteoarthritis?
Why does one person have it much more severely than another person?

The endless "why" questions traverse the minds of people who suffer with arthritis, the people who care about them, the doctors who treat them, and the researchers who strive to find the answers.
Researchers and scientists are focused on what causes arthritis and what predisposes certain people to the disease. Many things have been considered as contributing to the cause of arthritis, including:
viruses
environmental factors
diet
other triggers
These and other factors have all been considered as relating to the cause.
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During the past few decades, genetics has become a more prominent area of arthritis research.
HLA-B27 Gene
A major genetic link was discovered back in the 1960's between the gene HLA-B27 and the spondyloarthropathies, a group of diseases affecting the spine and other joints.
90 percent of people with ankylosing spondylitis have the HLA-B27 gene.
7 percent of the general population have the HLA-B27 gene.
Scientists are working hard to find the other genes involved in the spondyloarthropathies and other rheumatic diseases.
During the decade following the discovery of HLA-B27, scientists found an association between carriers of the HLA-DR genes and increased risk of rheumatoid arthritis. It is believed that HLA-DR contributes to autoimmune disease, conditions caused by the immune system fighting the body it is supposed to protect. Other genes also are suspected of being major factors in the evolution of rheumatoid arthritis.

North American Rheumatoid Arthritis Consortium
The North American Rheumatoid Arthritis Consortium (which consists of 12 medical centers across the country, established and sponsored by the Arthritis Foundation, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the National Institute of Allergy and Infectious Diseases) has been analyzing clinical findings and genetic material from 1,000 pairs of siblings who both have rheumatoid arthritis. By testing 400 different genetic regions, researchers hope to identify specific genes associated with the rheumatoid arthritis.

HLA-DR4 Gene
The HLA-DR4 gene, which has been associated with rheumatoid arthritis, has also shown involvement inLyme disease. Lyme disease is caused by a microorganism which is transmitted to humans via deer ticks. Among the symptoms which can develop from Lyme disease are:
joint pain
inflammation
arthritis
People who have the disease more severely and do not respond well to the antibiotic treatment are more often found to have the HLA-DR4 gene. It has been theorized that once the microorganism moves to the joints, the immune response against it cross reacts with the person's own joint tissue in people who have the HLA-DR4 gene, leading to an autoimmune reaction.

Genetic Mutations
Other research has led to the discovery of a genetic mutation which causes osteoarthritis in some people. Several members of a family who had early onset osteoarthritis were found to have a genetic mutation in type II collagen. The mutation caused premature breakdown of joint cartilage in the affected family members. Since this discovery other genetic mutations in other families have been found and even more mutations are thought to exist. It is suspected that 25 percent of people with osteoarthritis have a specific gene mutation directly responsible for their osteoarthritis.

Is Arthritis All In The Family?
Researchers are not ready to declare genetics or familial factors as the sole cause of arthritis and related diseases. As more and more studies are done, the genetic factor seems more evident.