If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Ankylosing spondylitis

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Amy Fan.

Want to join the conversation?

Video transcript

- [Voiceover] We're going to refer to ankylosing spondylitis as AS. So you don't have to keep hearing me say this long thing. But if we go word by word just once, you'll see that ankylosing means fusion. So it describes the spine being fused together. Spondy, this first part of the word, refers to the spine. and then -itis anywhere is inflammation. So this is an inflammation of the spine and at the sacroiliac joint, actually, and it leads to the fusion of the area. There's some buzz words surrounding it. So one of them would be that it is the poster child for a group of different diseases that are referred to collectively as the seronegative spondyloarthropathies. Spondylo-, so again, that's the spine, and then arthro, which refers to joints in general, and then pathologies or illnesses. So what this means is that they are rheumatoid factor negative. They do not have rheumatoid factor. But they also can appear like rheumatic joint diseases because it's systemic and it involves the immune system. So speaking of the immune system, the other buzz word you need to know is HLA-B17. I'm sorry, I always say that. It's B27. Again, it's part of the immune system. It's an antigen on the surface of the cell that can be recognized by T-cells, which can recruit things to attack it. So this is the autoimmune component of the disease. This HLA-B27 association actually exists for the seronegative spondyloarthropathies in general, but here, in particular, for AS you should remember that connection. And then, just a little background information on the group of people that tend to get this. Remember, nothing is absolute, but if we're looking for patterns, it's going to be males and relatively young ones, actually, really young ones, from 15 to 45 is going to be the mean or the biggest group of people who get AS or that's when it's diagnosed the most. So the name kind of tells us what symptoms are characteristic. We have this fusion of the spine. I drew it kind of like here, because it can be in the middle of the back, more commonly in the middle to lower back of the spine. So look at the curvature of this, this natural curvature of the spine. So this is a person looking to the right at the screen. The head is over here. As you come down the back, it kind of curves in here, and the pelvis is down here. This whole thing is supposed to allow you to bend forward, bend backwards. If you look at the area here, you should be able to actually bend forward more than you can bend backwards. But the important part is that with ankylosing spondylitis you don't have that kind of free movement because you have fusion, and this is why one of the nicknames for the symptom is a bamboo spine. Like a piece of bamboo, instead of a bendable stack of bones. Bamboo spine. So while bamboo spine is what we think of immediately when we see AS, remember that it's a systemic autoimmune disease, which means it affects, it could potentially affect everywhere in the body. And this person might have fever, malaise, other nonjoint problems. When we're talking about joints, aside from the spine, it also tends to affect the iliosacral spine. Iliosacral. I haven't drawn the pelvic bowl of bones here, but this is the joint that, think of it how your leg, your thigh attaches to your body. So the pain and inflammation can actually go down, following the spine, and can shoot into the legs, and the iliosacral joint itself can be affected as well. So the pain, I think of it as this area for joint pain. If we want to talk about systemic effects, it has a pattern of affecting two other places. One is eyes, particularly uveitis, and the other one is the aorta. So the aorta is the big pipe, the big hoop. This is just the four chambers of the heart, and this is the left atrium, the left ventricle. This is not anatomic, because technically the aorta comes kind of above the heart, comes out this way, but just drawing our little cartoon here, just to show you the aorta is this pipe that comes off of the left ventricle, and it pumps blood to the whole body. This is where oxygenated blood, where we think of red blood with oxygen in it, reaches the rest of the body. So if we have inflammation in the aorta here, you'll see at least two cardiovascular problems. First in the eyes we have uveitis. You can have redness, inflammation. This uveitis is kind of near the front chamber of the eyes. It can lead to redness, pain, discomfort. They can be afraid of light. They can see things floating in front of their vision that's not really there or not physically there. So that's uveitis, and it has an HLA-B27 association as well. And then in the aorta, like I said, this is where all the blood goes to the body. So if we have inflammation, inflammation in the walls of the aorta here, we can get what's called an aneurysm. An aneurysm is kind of like if you have a pipe here and you have some slack in the walls or some weakening in the walls, kind of bulges out here and becomes a weak point in the pipe. This can happen in our blood vessels all over the body, but if it happens here, this where the heart and the aorta are connected is the aortic valve. Very important valve that prevents the blood from flowing this way, the backflow into the heart. So if you have uveitis, you might have a stretching or an aneurysm near the opening here, near the valve. This part is just slack, and the valve can't close properly. And then what you get is some backflow into the chamber of the heart. And we use green to show backflow. So red, forward flow. Green is back. So not only is the body not getting enough blood, but the heart has to pump extra volume because each time what's pumped out comes back in. So this can lead to a serious problem in the heart, and we call it aortic regurgitation, meaning from the aortic valve there's backflow. Regurgitation. This is a side effect of the aortitis, but it's also it's own disease. Oh, I forgot to write out aortitis, aortitis. If you realize the pattern here, -itis. Itis in spondylitis, everything -itis means inflammation. Unfortunately, AS is very difficult to diagnose. DX for diagnosis. Because the symptoms, even though it looks like I've demonstrated a pattern here, it really can occur anywhere. It can just look like plain old osteoarthritis for years. So it's a tricky thing to diagnose, and there's different ways to go about it, different levels. So we can start with an x-ray. The bamboo spine, if it's already fused, we can see it. There might be blood tests, because the blood will show us, there's no AS blood test, but it will show us how much inflammation is there. For example, the erythrocyte or red blood cell sedimentation rate. This is a marker for inflammation. So is the C-reactive protein. So these are also nonspecific to AS, it could be any autoimmune disease, but at least it will help us know we're dealing with an autoimmune disease and not just wear and tear. There's also genetic, because this disease seems to have a pretty genetic pattern. Also, the coding for HLA-B27, the coding for the antigen, we can trace that as well. And then there's something I guess we don't really use to diagnose AS, but we do use it to track how it's progressing, how fast and how bad, and it's called the Bath, which is the place in England where it's discovered, Ankylosing Spondylitis Disease Activity Index. What a mouthful. Everything is an acronym. But this index allows us to again track how this patient is doing over time, how they're doing with their treatment. And speaking of treatment, managing AS can seem, can look actually a lot like managing rheumatoid arthritis or the autoimmune diseases because the principle is the same. You need to reduce inflammation. There's a class of different drugs that with different mechanisms but they're grouped together as disease-modifying anti-rheumatic drugs, because it used to be developed for rheumatoid arthritis. So what's special about them is even though they go about it in different directions, it actually slows the progression of the disease, not just treat the symptoms. And we're going to use this for AS as well. There's tumor necrosis factor, which is something that causes inflammation in the body. It's basically something that can program a cell to kill itself, which can be helpful in preventing cancer within our body, but here it's just acts to the inflammation. So TNF inhibitors can be used, again to reduce the inflammation going around in the body. We can use NSAIDs. These are the over-counter, you think of probably as pain meds, for example, your ibuprofen. And they not only treat the pain, because the fused spine and everything can be really painful, they can also reduce inflammation. And then stronger pain meds as well, depending on the level of discomfort. So, as you see, the theme here is to decrease inflammation. That's the most basic ankylosing spondylitis in a nutshell. Remember that it can be similar to rheumatoid arthritis, in terms of affecting the whole body and a lot of inflammation. But the fact that it fuses and affects the spine, the eyes, the heart, and the fact that it does not have rheumatoid factor makes it different.