Psoriasis and celiac disease, conditions affecting the skin and digestive system, share an intriguing connection. Research highlights their common biological mechanisms, diagnostic complexities, and integrated management approaches.
The Shared Biological Basis
A significant link between psoriasis and celiac disease lies in genetic predispositions, particularly within the human leukocyte antigen (HLA) system. Both conditions are strongly associated with the HLA-DQ2 and HLA-DQ8 genes, which play a role in immune system regulation and are found in over 90% of celiac disease patients. These genes influence how the immune system recognizes and responds to certain antigens, including gluten peptides in celiac disease, and may contribute to the immune dysregulation seen in psoriasis.
Immune system dysregulation is a key aspect of both conditions, involving inflammatory pathways and T-cell activation. In psoriasis, T-helper 17 (Th17) cells involve producing pro-inflammatory cytokines like interleukin-17 (IL-17) and interleukin-23 (IL-23), which stimulate neutrophil and macrophage infiltration in the skin. Similarly, celiac disease involves T-cell activation in response to gluten, leading to intestinal inflammation.
The concept of gut permeability, often referred to as “leaky gut,” and the gut microbiome’s influence also contribute to systemic inflammation affecting both the skin and the gut. Alterations in the gut microbiota, known as dysbiosis, have been observed in psoriatic patients, resembling changes found in inflammatory bowel diseases. This increased intestinal permeability can allow bacterial products to enter the bloodstream, potentially promoting chronic systemic inflammation that impacts distant sites like the skin.
Identifying Celiac Disease in Psoriasis Patients
Diagnosing celiac disease in individuals who already have psoriasis can be challenging, as symptoms may be subtle or atypical. Common digestive symptoms of celiac disease include bloating, diarrhea, and abdominal pain. However, non-digestive symptoms such as fatigue, anemia, and joint pain are also prevalent and might be overlooked or mistakenly attributed to other causes in a patient already managing psoriasis.
The diagnostic process for celiac disease begins with blood tests for specific antibodies. The anti-tissue transglutaminase IgA (tTG-IgA) test is the primary initial serologic test, showing a sensitivity of 78% to 100% and specificity of 90% to 100%. Another important blood test is the endomysial antibody (EMA)-IgA test, which has a reported sensitivity of 86% to 100% and specificity of 97% to 100%.
If these serologic tests suggest celiac disease, a confirmatory small intestinal biopsy is performed. This involves an upper gastrointestinal endoscopy to obtain tissue samples from the duodenum, which are then examined for characteristic damage to the gut lining, such as villous flattening and crypt hyperplasia. It is important that patients continue to consume gluten before testing, as a gluten-free diet can lead to false-negative results.
Managing Psoriasis with Concurrent Celiac Disease
For individuals diagnosed with both psoriasis and celiac disease, strict adherence to a lifelong gluten-free diet is the primary treatment for celiac disease. This dietary change involves avoiding foods containing wheat, rye, and barley. Following a gluten-free diet helps to heal the intestinal damage caused by celiac disease and can reduce systemic inflammation in the body.
While not a direct treatment for psoriasis, a gluten-free diet may influence psoriasis symptoms by reducing this underlying systemic inflammation. Some studies have indicated that psoriasis patients with elevated antigliadin antibodies, even without a confirmed celiac diagnosis, showed improvements in their skin after adopting a gluten-free diet. However, more research is needed to determine the full extent of this benefit and identify specific patient populations who would most benefit.
Continued medical management of psoriasis remains necessary, encompassing topical treatments like steroid creams, phototherapy using ultraviolet light, or systemic medications such as methotrexate or biologics. A multidisciplinary approach is beneficial, involving dermatologists for psoriasis management, gastroenterologists for celiac disease, and dietitians to guide strict adherence to the gluten-free diet. This collaborative care helps ensure comprehensive treatment for both conditions.