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Kawasaki disease: diagnosis and treatment

Video transcript
Voiceover: Let's quickly go over the symptoms and signs that you see in Kawasaki disease and we'll go ahead and do that by taking a look at this little Kawasaki man that I'm drawing right here. Patients with Kawasaki disease have red eyes which is known as conjunctivitis. Conjunctivitis. Just means red eyes. Patients with Kawasaki disease may also have a rash on their body. This rash can be found on their back, on their chest, on their abdomen. Really somewhere central on their body. Patients may also get something known as adenopathy. Adenopathy is just lymph nodes swelling. In Kawasaki disease, the lymph nodes that are particularly swollen are the cervical lymph nodes. Cervical just means neck. Lymph nodes in the neck are swollen. Patients are sometimes known to have a strawberry tongue and the tongue gets bright red and very swollen with some bumps on it. It kind of looks like a strawberry. Patients are also noted to have what's known as desquamation of the hands and the feet. The hands and the feet may have what's known as desquamation. Desquamation just means peeling. The squamous epithelium, the cells that line the skin are falling off. It kind of peels off. You might see this peeling and it usually starts underneath the nailbeds and proceeds from there. Of course, the cardinal symptom of Kawasaki disease is a fever. The patient appears to be burning up. His fever has been lasting for over five days. When I'm driving my Kawasaki motorcycle I'm actually not a very good driver so when I drive it I'm actually likely to CRASH and BURN. This mnemonic will help you remember Kawasaki disease because these are the symptoms that you see in Kawasaki disease. Coincidentally, these symptoms allow you to reach the diagnosis. Patients with at least four out of five symptoms along with the fever that's lasted for over five days can be diagnosed with Kawasaki disease. Just because they have these CRASH symptoms and a fever that's lasted over five days does not necessarily mean this is Kawasaki disease. Let me give you a specific example. Let's take the example of streptococcal infections. Streptococcus is a type of bacteria and kids as you know are very susceptible to bacterias and viruses because they're always playing around and getting dirty, and touching different things that they shouldn't. Now strep throat also known as streptococcal pharyngitis. Pharyngitis is inflammation in the throat or in the pharynx usually just has lymph node swelling and a sore throat with really no fever. However, this can proceed to what's known as Scarlet fever. Now Scarlet fever not only has lymph node swelling but you can also get a rash on the chest. you can have a strawberry tongue, you can definitely get a fever and towards the end of the illness as it's going away, Scarlet fever can give you peeling on the hands and the feet. This is already maybe three to four symptoms. Streptococcal infection leading to Scarlet fever helps you understand why trying to look for four symptoms is very important to try to diagnose Kawasaki disease. It also illustrates the importance of looking for other diseases such as streptococcus and ruling them out before you can diagnose Kawasaki disease. Now there's also a more tricky form of Kawasaki disease that is known as atypical or incomplete Kawasaki disease. Atypical or incomplete Kawasaki disease is when you have three or less of these classical symptoms of Kawasaki disease. Now with high clinical suspicion of atypical or incomplete Kawasaki disease, the next step would be to get an ESR or a CRP. ESR stands for erythrocyte sedimentation rate and CRP stands for C-reactive protein. These names themselves are not particularly important to remember. A lot of times they're just referred to as ESR or CRP in the clinic. What's important is that these are signs of inflammation. Kawasaki disease is a vasculitis which means vessel inflammation. Searching for inflammation gives more credence to the idea that this could be Kawasaki disease. ESR should be elevated to above 40 mm per hour and CRP will be elevated above 3 mg/dL. Elevation of ESR or CRP means likely inflammation. To confirm this the next step is to get supplemental labs. These may include labs such as elevated ALT in the blood, elevated platelets in the blood, elevated white blood cells in either the blood or the urine or decreased albumin. Now I wouldn't get too bogged down with these supplemental labs. The important thing to remember is that if you have greater than or equal to three of these supplemental labs, you can diagnose Kawasaki disease and you'll treat the patient. If you have less than three supplemental labs then you're gonna need to take a look at the heart using a heart ultrasound. This heart ultrasound is also known as an echocardiogram. It allows physicians and practitioners to view the heart. Now why are we taking a look at the heart in this disease? In Kawasaki disease it's a vasculitis that can actually affect the blood vessels of the heart. Getting that ultrasound of the heart is very important to make sure that the patient doesn't have more severe symptoms of Kawasaki disease. What will you see with the heart ultrasound also known as an echocardiogram? Let's see, what do we have in the heart? First of all we have blood vessels which we were just talking about. We also have valves. We have the heart muscle itself which allows the heart to contract. Lastly around the heart we have a thin sac that surrounds it. This is called the pericardial sac. What is this used for? The pericardial sac is actually filled with a fluid and this fluid that surrounds the heart actually keeps it lubricated. It's kind of like keeping a machine lubricated so that the parts don't cause too much friction and cause damage to the parts. The peridcardial sac holds this fluid that's important to keep the heart functioning without friction. Our echo will allow us to see if there's any damage to these parts of the heart. First of all damage to blood vessel walls will cause it to weaken and because there's too much pressure on the inside it bulges out. This bulging of a weakened blood vessel is called an aneurysm and an echocardiogram can pick this up. Blood vessels a lot larger in their diameter than they should be. Now remember along with aneurysms we have blood vessel thrombosis. What is thrombosis? The damage to these blood vessels we have clots forming and these clots block blood from flowing forward through the heart. Without blood heart cells and heart muscle can die. Now let me back up just for a second. Remember that blood flows forward through valves however, when heart valves are damaged you can actually get back flow through the heart. This back flow is known as regurgitation or regurgitant flow. It's essentially a sign that valves are faulty and this can be caused by damage to blood vessels because muscles that keep the valve working in one direction are damaged. Another abnormal finding we can see is decreased contractility or in other words decreased ability for the heart to pump effectively. Remember these blood vessel thrombosis or clots in the heart? The clots are preventing blood flow from getting through to some of the heart muscle. This heart muscle may actually die because it's not getting the blood it needs to survive. This is also known as a myocardial infarction. This is a very severe complication we're hoping to avoid because there's no fixing heart muscle once it's damaged. Finally the most severe finding we can see with an echocardiogram is rupture of blood vessels. If these aneurysms get so weak that the blood vessel can no longer keep the blood in it it will rupture and spill out of the heart. When this happens, blood will pool and collect in the pericardial sac. A collection of fluid is also known as an effusion. You may actually hear the term pericardial effusion. That just means there's fluid that's around the heart and in this case, the fluid is blood. Rupture's another very severe consequence of Kawasaki disease. If a patient has any of these abnormalities on echocardiogram, to prevent further complications we need to look into the treatment of Kawasaki disease. Once you reach the diagnosis of Kawasaki disease there are two treatments. By inactivating platelets that cause clots. We decrease inflammation. The decrease of clot formation is extremely important because going back up here, remember we have a lot of clots being formed and this can lead to the severe heart attack or myocardial infarction. Preventing clot formation can prevent the irreparable damage of a heart attack. Next you want to further stop the disease process by giving IVIG. IVIG stands for intravenous. That's just how the medication is delivered. Immunoglobulins. Immunoglobulins are just antibodies. Those little Y-shaped proteins that are believed to cause all these damaging Kawasaki disease. Wait a second, why am I giving more antibodies? Remember the Kawasaki disease antibodies are the ones that are targeting the blood vessel. These guys are the bad ones that are causing damage. All the rest of these ones, these greens ones that I've drawn here are fine. This is the IVIG that we're giving. Why does giving more antibodies that are not the damaging antibodies helpful in the treatment of this disease? The answer to that is not quite known but we have some ideas. The first ideas is that the white blood cells and the immune system are overwhelmed by all of these other antibodies. They spend all their time attaching to these and these antibodies are not activated. They're not going to cause any damage. It prevents the white blood cells from attaching to these activated Kawasaki antibodies. Another thought is that these antibodies are directly deactivating all the bad antibodies. Maybe the good antibodies, the IVIG that you're giving are somehow blocking the antibodies that are causing vasculitis. Another thought is that the white blood cells sends so many antibodies. They say, wait a second, this is too much. They decrease their responsiveness and give more of an anti-immune effect. Lastly, another thought is that a large amount of antibodies increases the removal of all antibodies in the system. This leads to clearance of all of these. The good antibodies and the bad ones. Whatever the case, IVIG is known to decrease the inflammatory effects that we see in Kawasaki disease. It's very important to treat with these before the heart gets damaged.