Ankylosing spondylitis and Crohn’s disease are both caused by inflammation. While the first is inflammation of the joints the latter is inflammation of the gastrointestinal tract. And the interesting thing about the two is that there are quite a few matters that overlap between the two diseases.
In fact it has been seen that quite a number of people suffering from ankylosing spondylitis have been diagnosed with Crohn’s disease. Sometimes ankylosing spondylitis and peripheral arthropathy of inflammatory nature can be complications of Crohn’s disease too. To understand both ankylosing spondylitis and Crohn’s disease and how they are related it is important to know about these conditions.
Ankylosing spondylitis is a disease of chronic inflammation and falls in the group of diseases referred to as Spondyloarthropathy of SpA in short. Such diseases are characterized by the inflammation of enthuses or the point where the cartilage and the bones meet. In such cases the factors responsible for rheumatism and other factors like subcutaneous nodules are generally absent. The cause of such conditions has been linked with an antigen called Human Leukocyte Antigen or HLA-B27 in short and a possible genetic connection.
Ankylosing spondylitis starts with inflammation of the sacroiliac joints (joint between the vertebrae and pelvis) but peripheral joints and other structures not related to joints get affected too. The areas of the body that get mainly affected are the pelvis and the spine but hips, shoulder, the chest wall and the feet may also get affected. With time as the condition advances, there is a chance of the vertebrae getting fused permanently.
This is a disease of complex nature where the Gastro intestinal tract gets inflamed. The inflammation can be of granular nature and can sometimes affect elements lying outside the GI tract. Often extra-intestinal complications are seen in Crohn’s disease.
The patient suffering from Crohn’s disease may show symptoms like vomiting, pain, chronic diarrhea, weight loss and at a later stage may show rectal bleeding, fistulas of the anal region and its surroundings (perianal region), abscess in the ileum and colon as well as abnormality in the anal and perianal region.
Similarities between Crohn’s Disease and Ankylosing Spondylitis
First of all, both Crohn’s disease and ankylosing spondylitis are lifelong inflammatory diseases which can even cause death in the extremely rare conditions. But the interesting fact is that it has been seen that people suffering from irritable bowel disorder like Crohn’s disease often get SpA conditions like ankylosing spondylitis and also the other way round.
Scientists suggest that as both the diseases have genetic background, there is a strong possibility that both of these diseases share some common genes which may be responsible for the conditions. Bacteria and immunity imbalance also contribute to both of these diseases.
Link between Ankylosing Spondylitis and Crohn’s Disease
It has been established that people suffering from one of these diseases may get another. Immune response to bacteria can trigger both the diseases. A T-cell influenced immune response to the bacterial presence in the gut may produce antigens and other products which may eventually prove detrimental to the joints and the nearest joint to the guts get affected. That is why the sacroiliac joint (between the lowest vertebrae and pelvis) gets affected most of the times.
The immune response system in both the diseases produces inflammation triggered by a cytokine, (non-antibody proteins released by specific type of cells as a part of the immune response system of the body) termed TNF-α. It has been seen that administering inhibitors of this cytokine has significantly lowered the progression of the disease in both Crohn’s disease and ankylosing spondylitis.
Results of Anti TNF-α Therapy
Clinical trials of anti TNF- α therapy have shown some positive results in both the diseases. It has been seen that in case of ankylosing spondylitis the patient’s age and duration of the disease matters. So those in the younger age group with shorter duration of the disease respond better to the therapy. It has been also suggested that the therapy should not progress if the patient does not respond even after 6 to 12 weeks of treatment.
Drugs for Anti-TNF- α Therapy
Three drugs have been identified which are used commercially in the treatment of ankylosing spondylitis. They are infliximab, adalimumab and etanercept. Of these the last one is not used in Crohn’s disease. The use of the other two has showed quick reaction and can gradually help in discontinuation of corticosteroids. In case of Crohn’s disease, the drugs should be used only for induction therapy and for maintaining the remission process but not for treatment of episodic bouts of the disease. As this is a biological therapy, such episodic use may lead to development of antibodies against the agents.