A connection between psoriasis and celiac disease suspected for some
From July/August 2004 Psoriasis Advance
Have you ever wondered if something in your diet might be making your psoriasis worse? Many people have. There have been nearly as many theories about diet and psoriasis over the years as there have been people with psoriasis. But scientists have never convincingly demonstrated the effect of any particular diet on the disease. Now however, a growing body of research is beginning to establish that for a very small percentage of people with psoriasis, there may be an important connection between what goes in their mouth and what happens on their skin.
That connection could have everything to do with last night's heaping bowl of pasta-and this morning's cereal, the post-breakfast donut at the office and your lunchtime sandwich. All of these meals contain gluten, which is the insoluble component of grains such as wheat, barley and rye.
Some researchers believe that a very small subgroup of people with psoriasis may also have gluten-sensitive enteropathy, also known as gluten intolerance or celiac disease. People who have celiac disease may have mild to severe damage to the lining of the small intestine, damage that can cause chronic diarrhea, food absorption problems and nutritional and vitamin deficiencies. According to the most recent studies, celiac disease may affect as many as 2 million Americans. Individuals with celiac disease may experience abdominal cramping and pain, bone and joint pain, bloating, flatulence and fatigue, among other symptoms.
No more pasta?
Researchers who have studied psoriasis and gluten intolerance believe that people with both diseases might significantly improve their psoriasis by using the only available treatment for celiac disease-a strict, limiting diet called the Gluten-Free Diet (GFD). This diet requires long-term, complete avoidance of gluten, which requires a radical change in the eating habits of most Americans.
Avoiding gluten while on the GFD means giving up common foods such as barley, beer, cereals, anything made with wheat flour, and pasta. Such a diet is definitely a complete lifestyle change, and results may appear only after weeks or months of strict adherence to the diet. Gerald Krueger, M.D., professor of dermatology at the University of Utah, says no one should be misled about the GFD. "It is a very harsh diet. People with severe celiac disease will tell you it is very difficult."
Psoriasis and gluten research
A 1993 study by Swedish scientists led by Gerd Michaelsson, M.D., Ph.D., professor emeritus at Uppsala University in Uppsala, Sweden (see below for interview with Dr. Michaelsson), found that 16 percent of patients with psoriasis had increased antibodies to gliadin (the proteins in gluten to which some people have a reaction). Increased levels of these antibodies, called AGA, are one marker of celiac disease.
The same researchers performed another study, published in the British Journal of Dermatology in 2000, which evaluated the effect of a gluten-free diet in 33 people with psoriasis who were AGA-positive compared to six people with psoriasis who were AGA-negative. Participants followed the GFD for three months, followed by three months on their ordinary diet. Thirty of the 33 AGA-positive patients improved on the GFD, while none of the six AGA-negative patients improved on the diet. When the AGA-positive patients went back to their ordinary eating habits, psoriasis got worse for 18 of the 30 who had originally improved.
According to Dr. Krueger, it is encouraging to note from these small trials that many of the psoriasis patients who had tested positive for AGA did improve on the GFD. "It does look like there is an increased frequency of celiac disease among people with psoriasis," says Dr. Krueger. "I do think there could be something there, given that both psoriasis and celiac disease appear to be Th-1 type immune-mediated diseases." Both psoriasis and celiac disease are believed to be diseases driven by hyperactive, or inappropriately activated, T cells-in the skin for psoriasis, and in the gut for people with celiac disease. This is the intriguing connection that has scientists looking at the two diseases for other links in both cause and treatment.
Connection still in doubt
However, simple math dictates that it would be surprising if there weren't some people with both diseases. "Indeed," Dr. Krueger says, "there is a certain small percentage of people in the general population with celiac disease, and a certain small percentage of people in the general population with psoriasis, so one should not be surprised to find a significant number of people who have both. The challenge is to determine if the connection is real. The difficulty in determining a final truth is one of numbers-numbers of patients and numbers of dollars. It can be very difficult for researchers to gather enough patients to study a rare subgroup of patients in a disease that only affects about 2 percent of the population in the first place. And it is very, very expensive."
Meanwhile, it is very important to discuss celiac disease and the GFD with your doctor before changing your diet or your treatments. Symptoms may or may not be present for people with both diseases. Dr. Michaelsson believes that in fact many people with psoriasis who are AGA-positive and who could potentially be helped by the GFD may have no celiac symptoms, but instead may have what she calls "silent celiac disease.
"If you believe that gluten intolerance may be an issue for you, particularly if you have uncontrolled moderate to severe psoriasis or palmoplantar pustulosis, Dr. Krueger recommends that you discuss the situation thoroughly with your doctor. Talk about whether a screening for the markers of celiac disease (including anti-gliadin, anti-endomysial antibodies and anti-tissue transglutaminase) might be recommended. These markers are present in the blood of a person with celiac disease who has been exposed to gluten, but the markers disappear when gluten is removed from the diet.
It is important to consult with a doctor and get the appropriate tests before starting a GFD, because following the GFD before having the proper blood tests can jeopardize the tests' accuracy. Many doctors will want to follow positive blood tests with a biopsy of the intestine to confirm celiac disease. For psoriasis patients who have been diagnosed with celiac disease, Dr. Krueger agrees with Dr. Michaelsson's recommendation that it would be worthwhile to try a GFD.
Three organizations that may also be able to provide information
are:
The links above take you off the Psoriasis Foundation Web site. The Psoriasis Foundation does not endorse or accept any responsibility for the content of external Web sites. Click here for complete terms of use.
Psoriasis and gluten intolerance
An interview with Dr. Gerd Michaelsson
What are the key pieces of evidence that link celiac disease (or gluten intolerance) and psoriasis?
First - most patients with psoriasis are not gluten intolerant. However, there is a subgroup with silent celiac disease/gluten intolerance and it is important to identify these patients, as there is a chance to considerably improve the skin lesions on the gluten-free diet (GFD). In some patients there may be a total or nearly total clearance on the diet. When gluten is reintroduced there is a flare up of the psoriasis. The effect of the diet also seems to be very good in the type of psoriasis called palmoplantar pustulosis (PPP) - again with recurrence when gluten is reintroduced. Otherwise, in PPP the main focus is on the role of smoking, as 95% of PPP patients are smokers at the onset of their PPP. In looking at patients with psoriatic arthritis and with evidence of gluten intolerance, there is an improvement both of the skin lesions and the arthritis. But the effect on the arthritis is less impressive than that on the skin, which may indicate that there may be additional causative factors involved in the arthritis.
In your opinion, what percentage of people with psoriasis and/or psoriatic arthritis are affected by the link?
About 16% of patients with psoriasis vulgaris have serum antibodies against gliadin, which is a fraction of gluten. It is interesting that we have found no patients with psoriasis vulgaris, without arthritis, who have a previously diagnosed celiac disease (but also see below concerning psoriatic arthritis). Probably patients with celiac disease adhering to a strict GFD do not develop psoriasis or the psoriasis clears on the diet and these patients do not need to see a dermatologist.
Not all psoriasis patients with antibodies to gliadin have classical celiac disease, which is characterized by a damage of the villi in the intestinal mucosa and pronounced inflammation. Many of the patients have only mild changes in the intestine with very discrete inflammation. Still, they can improve on GFD. However, the most dramatic improvement of the psoriasis takes place in those with the most pronounced changes in the intestinal mucosa. Some of these patients also have serum antibodies against the enzyme tissue transglutaminase.
Among patients with arthritis the percentage with antibodies to gliadin is the same as in those with psoriasis vulgaris but in addition we found that 4% had previously diagnosed celiac disease which again indicates that the arthritis does not respond in the same way to GFD as the skin.
The highest percentage of serum antibodies to gliadin (20%) is found in patients with PPP. Our preliminary data indicate a very good response to the GFD in these patients.
What do you think is the most likely explanation for the connection between the two diseases? Is it likely to be genetic, or caused by other factors (i.e. immune-mediated, t-cell activation, etc.)?
Psoriasis patients with gluten intolerance may belong to a genetic subgroup with increased risk for psoriasis, celiac disease/gluten intolerance and thyroid disease - the latter association is particularly common in women with PPP. Possibly there may be one or several autoantigens which are relevant for the inflammation in psoriasis. One of these possible autoantigens may be the enzyme tissue transglutaminase which is expressed in proliferating small blood vessels but also involved in the processing of gluten. The expression of this enzyme is increased in the blood vessels of psoriatic lesions and this expression is decreased when the patients are on GFD. At the same time there is a decrease in the number of proliferating cells in the skin lesions. Further studies are needed to clarify this issue.
Would you recommend patients with psoriasis or psoriatic arthritis look for any particular symptoms, or take any particular actions?
In our patients with previously unrecognized gluten intolerance, we found that none of them had an increased history of gastrointestinal complaints versus those who were not gluten intolerant. We recommend that patients with moderate to severe psoriasis or palmoplantar pustulosis be screened for the presence of serum antibodies against gliadin and tissue transglutaminase and for the level of serum IgA (if serum IgA is low the antibody screening may give false negative results). It should also be observed that in 10% of patients found to have celiac disease there are no antibodies in the serum. Other markers which may indicate the presence of celiac disease are low levels of iron, zinc and folic acid, but in patients with only mild intestinal changes these parameters are usually normal. The costs of the screening are low and the results may be very rewarding. Thus, our first observed patients with psoriasis and silent celiac disease has been free from psoriasis for 25 years!
|
