Dr. Schär Institute

The authors note that celiac disease-specific antibodies such as IgA anti-gliadin, reticulin, glutaminase, and smooth muscle endomysium have been found in patients with psoriasis and other autoimmune diseases (systemic lupus erythematosus (SLE), rheumatoid arthritis, and Sjögren’s syndrome), and that the level of these antibodies was correlated to the severity of the psoriasis.
 
Various epidemiological studies have also established a link between the two conditions. A percentage of patients with psoriasis, varying between 0.2% and 4.3%, depending on the study, may present with concomitant celiac disease. A broad epidemiological study conducted in Sweden demonstrated that patients with celiac disease are at increased risk for psoriasis, both before and after the diagnosis.
 
The authors note, however, that other studies showed no link between psoriasis and celiac disease, either at clinical or serological level.

 

The links between psoriasis and celiac disease

 So what are the possible mechanisms linking celiac disease to psoriasis? The authors suggest four factors:

Links between psoriasis and celiac disease

• Vitamin D deficiency
• Th2 immune response, as well as Th1 and Th17 cell responses [cutaneous lymphocyte-associated antigen (CLA)]
• Genetic background
• Increased intestinal permeability

The malabsorption associated with celiac disease may predispose to Vitamin D deficiency, and the gluten-free diet used to treat celiac disease is often lacking in this vitamin. It is well-known that Vitamin D deficiency predisposes to psoriasis; exposure to sunlight and the administration of topical vitamin D analogues in the form of creams are beneficial to psoriatic patients.
 
From an immunological standpoint, celiac disease is generally associated with the Th2 response. However, Th1 and Th17 cells, the lymphocyte subpopulations involved in the development of psoriasis, also play an important role in the pathogenesis of this condition. Skavland et al. have recently demonstrated that certain wheat antigens can trigger an immune response in psoriatic patients significantly more often than in control subjects without psoriasis, inducing expression of the cutaneous lymphocyte-associated antigen.
 
In regards to the possible common genetic background shared by celiac disease and psoriasis, some studies have identified genetic susceptibility in eight genes which regulate the innate and adaptive immune response.
 
Finally, an increase in intestinal permeability, which is a characteristic of celiac disease, has also been found in patients with psoriasis.

 

The benefits of a gluten-free diet

The authors point to a large body of evidence suggesting that patients with psoriasis, both those with concomitant celiac disease and those with asymptomatic gluten intolerance, may benefit from a gluten-free diet. In a study on psoriatic patients who tested positive for anti-gliadin antibodies (AGA), a three-month gluten-free diet led to a significant reduction in the affected area of skin, PASI scores, and anti-gliadin antibody titre (AGA). The authors point out that 50% of the patients positive for AGA showed no endoscopic evidence of celiac disease prior to adopting a gluten-free diet, suggesting that this diet may also be beneficial for those psoriatic patients with asymptomatic gluten sensitivity.
 
Another study showed that the adoption of a gluten-free diet led to a decrease in the expression of transglutaminase in AGA-positive patients with psoriasis. Finally, a number of reported cases have documented a complete resolution of skin lesions following the administration of a gluten-free diet to patients suffering from psoriasis with serological evidence of intolerance to gluten.
 
The authors conclude that overall, these results suggest that a gluten-free diet may have beneficial effects for the majority of patients with psoriasis who have tested positive for celiac disease-specific antibodies.