suffering from Athritis?
Types of Arthritis
Facts about Arthritis
The role of genetics in the manifestation of various arthritic diseases
There appears to be no single cause of most forms of arthritis. Rather, the disease probably arose through the complex interactions of many different factors. One such factor appears to be genetics. Genetics is a type of science that focuses on the hereditary transmission of different characteristics among families. Current research has demonstrated that genetics play an integral role in the development of various types of arthritic diseases such as osteoarthritis, ankylosing spondylitis, psoriatic arthritis, rheumatoid arthritis, fibromyalgia and gout.
Numerous studies have demonstrated that genetics play a major role in the development of osteoarthritis. One such study demonstrated that genetic factors make a significant contribution to the development of osteoarthritis of the hip in women and account for approximately 60% of the variation in population susceptibility to the disease (1). Another study further illustrated that genetics influence the development of osteoarthritis. This study was based on 49 families who had at least one sibling affected with osteoarthritis. The offspring of these 49 families were 3.5 times more likely to develop osteoarthritis in their lifetime compared to those people without the same family history (2). Another study demonstrated that genetic influence ranges from 39-65%, free of known environmental variables, in the development of hand and knee osteoarthritis (3). These and other studies illustrate the role of genetics in the development of osteoarthritis.
Ankylosing spondylitis is another type of arthritis which has a genetic component associated with its disease manifestation. It has been shown that the presence of the genetic marker HLA-B27 increases the likelihood of developing ankylosing spondylitis. One study suggests that people who carry this HLA-B27 marker have a 20-fold higher risk of developing spondyloarthropathies, such as ankylosing spondylitis and reactive arthritis, than those lacking the genetic marker (4). In fact, about 90% of children who have juvenile ankylosing spondylitis carry this genetic marker and 50% of children with juvenile psoriatic arthritis carry it as well. Most recently, however, it has been shown that HLA- B27 homozygotes (i.e., individuals with identical alleles at a particular gene location) have a moderately increased risk of ankylosing spondylitis compared to HLA- B27 heterozygotes (those with different alleles at a particular gene location). Otherwise, having this HLA-B27 marker did not appear to significantly affect the clinical manifestations of ankylosing spondylitis. This study also showed that persons who were HLA-B27 positive had an earlier onset age of ankylosing spondylitis than people who were HLA-B27 negative (5).
The genetic involvement suggested in psoriatic arthritis is not limited to its association with the HLA-B27 marker. Various studies have been conducted on the possible hereditary transmission of this disease. A study conducted in the United Kingdom showed that a genetic locus on chromosome six is involved in the inheritance of psoriatic arthritis. Furthermore, this study demonstrated that more people with affected fathers, rather than mothers, have developed psoriatic arthritis (6).
Rheumatoid arthritis similarly involves a combination of genetic factors, including genetic markers as well as familial transmission. The marker HLA-DR4 is found in about 61% of people with rheumatoid arthritis (7). Current data on juvenile rheumatoid arthritis have shown that multiple genes, including at least one gene in the HLA region, influence the susceptibility to this disease (8). To determine the degree of inheritance of rheumatoid arthritis, various twin studies were performed. In a “twin study” identical twins that were raised in different environments are followed to assess the impact of environment versus genetics. If identical twins raised in different locations, by different families and even in different cultures express the same disease as adults, it is more likely that the disease has a genetic basis as opposed to an environmental basis. One twin study in Finland demonstrated that there is a 65% heritability rate in the manifestation of rheumatoid arthritis. Another study, conducted in the United Kingdom, showed that there is a 53% heritability rate in the development of rheumatoid arthritis (9). Both studies showed that there are definite genetic components in the development of rheumatoid arthritis.
The genetic involvement in the pathogenesis of fibromyalgia is not well established. Familial studies suggest that genetic and familial factors may play a role in the development of this disease. While the exact role of these factors remains unknown, it is likely that several genes participate in the expression of this syndrome.
Like fibromyalgia, it has been long known that the occurrence of gout has a hereditary component. Current research has shown that between 6 to 18% of people that are stricken with gout have histories of the disease in their family.
There are a variety of factors that contribute to the generation of arthritic diseases and the severity of their development. Environmental factors, lifestyle choice, and genetics all interact to trigger the onset of various arthritic diseases. Predisposition to a disease due to genetic markers or familial heredity does not guarantee the onset of a disease. Rather, these factors serve as lifestyle guidelines to prevent the disease from manifesting.
Authors: Svetlana Chernyavsky, B.A., New York College of Osteopathic Medicine, Old Westbury, NY
Ana Bracilovic, M.D., New York-Presbyterian Hospital, The University Hospital of Columbia and Cornell, New York City, NY