Autoimmune diseases run in families in two ways. If you have an autoimmune disease, you probably inherited the genetic susceptibility from your parents and could pass it down to your children. Similarly, within the extended family of autoimmune disorders, some are closely related and others more distant, depending upon the number of genetic markers they share. As it happens, celiac disease, an extreme form of intolerance to gluten, proteins found in wheat, barley and rye, is a close genetic relative of two painful, progressive and potentially disabling diseases of the joints, rheumatoid and psoriatic arthritis.
Rheumatoid and Psoriatic Arthritis
Both forms of arthritis occur when the immune system mistakenly perceives joint tissue as foreign and deploys antibodies to attack it. People with RA may or may not have other autoimmune conditions, but people with psoriatic arthritis always have psoriasis, a disfiguring skin disease. RA is estimated to affect about 1 percent of the population. According to the National Psoriasis Foundation, about 7.5 million Americans suffer from one of five types of this disease, and about 30 percent of those either have, or will develop, psoriatic arthritis.
Genetic Links to Celiac Disease
A Netherlands-U.K. study involving thousands of people with RA and celiac disease was published on July 31, 2009, in "Human Molecular Genetics." After comparing the genetic fingerprints of both diseases, researchers found four new common markers, confirmed the existence of two previously suspected, and hypothesized that others remain to be found. Five markers are directly involved in overall autoimmune function, and all six are located in regions of the chromosome implicated in several other autoimmune conditions, including psoriatic arthritis. The close proximity of these genetic identification marks suggests that people predisposed to one autoimmune disease are more susceptible to others, researchers concluded.
Gluten-Free Diet
At present, strict adherence to a gluten-free diet is the only available treatment for celiac disease, which affects about 1 percent of the population. In most cases, it is extremely effective in clearing up symptoms and reversing intestinal damage, allowing celiacs to live normal lives. Because celiac disease has been linked to many other conditions, including schizophrenia, depression, multiple sclerosis, autism and lupus, gluten-free diets might prove to be beneficial to some people suffering from those, although most evidence is still anecdotal. However, a study published on March 18, 2008, in "Arthritis Research and Therapy" reported significant improvements in the conditions of 38 people with RA after only three months on a gluten-free vegan diet.
Hope on the Horizon
A University of Chicago study published in "Nature" on March 10, 2011, combined data from patients treated at the university's Celiac Disease Center with experiments on mice genetically engineered to be susceptible to celiac disease. Levels of two chemicals produced by the body, interleukin 15 and retinoic acid, are elevated in both celiacs and people with RA. Researchers discovered that blocking the production of these chemicals prevented the onset of celiac disease in some mice and immunized those already affected against an autoimmune reaction to dietary gluten. If IL-15 lives up to the promise shown in this study, celiacs may be able to reap the benefits of the clinical trials now underway to determine whether IL-15 blockers are effective against RA. At the time of publication, though, there is no indication when these drugs might be approved.
References
- Mayo Clinic; Celiac Disease; Symptoms
- "Science Daily"; Human and Mouse Studies Sharpen Focus on Cause...; Feb. 10, 2011
- "Nature"; Abstract; Co-Adjuvant Effects of Retinoic Acis and IL-15 Induce...; R.W. DePaolo et al; March 10, 2011
- "Medscape Today"; The Genetics of Celiac Disease Is Complex;
- "Human Molecular Genetics"; Common and Different Genetic Background for RA and CD; Marieke J.H. Coenen et al, July 31, 2009
- National Psoriasis Foundation: About Psoriatic Arthritis
