In this lecture, we will discuss Kawasaki disease. This is commonly addressed on multiple choice tests.
So, Kawasaki’s disease is a multisystem inflammatory condition of medium-sized blood vessels.
The mechanism behind Kawasaki’s disease is not at all understood. Nobody understands why this happens.
That said, there are some significant differences between Japanese and American Kawasaki disease
that might shed some light on the pathophysiology. The disease was discovered in Japan,
hence the Japanese name. Retrospective studies have been used to try and determine what was happening
when we saw children who presented with coronary artery aneurysms. They then looked at all these
children who have all these symptoms prior to the development of the coronary artery aneurysms.
They put together a clinical criteria for the diagnosis of the disease. That said, the Japanese disease
and the American disease are so different that perhaps they are different diseases.
Children with Japanese Kawasaki tend to get much sicker and are much more likely to have giant aneurysms
that can be life threatening. These two diseases are treated differently on the two continents. We will focus
in this lecture on American Kawasaki disease. So, Kawasaki is a common vasculitis in children.
80% of children will have it before five years of age. However, a small percentage can have it even later,
even over the age of 10. It’s a self-limited initial inflammatory stage that ends about after 12-14 days
of significant inflammation. However, if untreated during the inflammatory stage, that child now has a risk
for development of coronary artery aneurysms which can absolutely be life threatening.
In children under one year of age who have the disease, they will have a worse prognosis
and be more likely to develop the coronary artery aneurysm. So, let’s go through the clinical criteria
for the diagnosis of this condition. One way to remember it is CRASH and burn. So, burn first.
These patients need at least five days of fever. If they have four days of fever and other criteria,
they may well have Kawasaki disease. But we typically will not treat the disease until five days.
The reason is that children who are treated early have actually an increased risk of developing
the coronary artery aneurysms that we are attempting to avoid. Now, let’s go through the CRASH part
of crash and burn. Each letter in the word CRASH stands for one of the five major criteria
for Kawasaki disease. C is for conjunctivitis. This is a limbic sparing, nonpurulent conjunctivitis.
R is for rash, any type of rash. A is for adenopathy, usually in the anterior cervical chain.
S is for strawberry tongue but realistically, it can also be dry, red, cracked lips, any sort of mouth
mucous membrane changes. H is for hands and feet, in particular, swelling although peeling does also count
as criteria in that under one age group who have fever for seven days and no other explanation for it.
So, for a diagnosis of Kawasaki, you need either four or five of these criteria plus the five days of fever.
The CRASH, four or five and the burn, you need five days of fever. So, the fever should be more than
37.5 degrees centigrade for at least five days. If the patient meets other criteria, early treatment
may be less effective. In general, one key thing about these systemic symptoms and this isn’t a criteria
but it definitely tips you over the edge in this questionable cases, children with Kawasaki are irritable.
They are fussy. They don’t want you to be near them. They are really fussy. They feel much better
after their treatment. Let’s look at this conjunctivitis. It will look a little bit like this. It’s basically
a non-purulent red eye, no pus, just red. The area around the limbus of the iris is spared.
The redness is more peripheral. So, it’s limbic sparing. Patients may have some photophobia
but that’s not necessary at all for the diagnosis. Oral mucous membrane changes include
the strawberry tongue. Can’t really see it too well here but this child definitely also has dry, red,
and cracked lips which are pathognomonic for the condition. The lymphadenopathy is usually unilateral.
It's usually in the anterior cervical chain. They have to have one node that’s at least 1.5 cm large.
The rash is nonspecific. It’s usually a maculopapular erythematous rash that looks like your typical
viral exanthem. It usually involves the trunk, the face, the extremities, or the diaper area.
The hands and feet condition may be red or just swollen. Sometimes a patient comes in on day four
of illness and the mom says, “Oh yes, three days ago, her hands were swollen. I just didn’t do
anything about it." That counts. A historical report of one of these findings counts in the criteria
for this disease. Here is an example of the peeling of fingers that can happen usually later in the syndrome.
Also, patients can get other symptoms which don’t define the disease but do happen. It may tip you
over the edge in a questionable case. Patients may develop an arthritis. We may get LFTs
because patient can have hepatitis. Rarely, patients can have the complication of gallbladder hydrops.
This is a clever question on a multiple choice test where they ask about severe right upper quadrant pain
in a patient with Kawasaki disease. This is a surgical emergency where the gallbladder may perforate
and result in peritonitis. So, here is a typical picture. It’s a good picture to look at when these symptoms
typically happen in the normal course of the illness. From the topline, you can see that the fever
will typically last more than five days. It may last even two weeks or longer but eventually, untreated,
that fever will resolve. The other symptoms that we used to define the condition such as the conjunctivitis,
the change in mucous membranes, or the cervical lymphadenopathy tend to happen early in disease.
The rash perhaps a little bit later. The extremity change at first is swelling and then later is peeling.
Complications typically happen a little bit later on such as the gallbladder hydrops. So, radiologic studies
and lab studies can be helpful especially in a patient who is a typical Kawasaki. A typical Kawasaki
is when patients meet either two or three criteria and we need other findings to help justify
whether or not we should be treating that patient. Labs that are indicating that something
more significant is going on include the ESR and the CRP. They may have an elevated white count.
Patients on CBC may also have a normocytic anemia. This is consistent with just an inflammatory process,
same thing with their thrombocytosis which is a high platelet count. Patients may have increased LFTs.
That is a sort of systemic hepatitis from the inflammation. One of the key things that show up on tests
frequently is sterile pyuria. When obtaining a urinalysis on a patient with this, we may notice
that they have increased white cells in their urine and suspect a urinary tract infection but nothing
ever grows out. One key subtle point about the sterile pyuria is it may be a urethritis rather than
a pyelonephritis. So, if a patient is catheterized to obtain the urine specimen, it may be missed.
These children should be bagged urine and a urine culture should not be sent because bagged urines
have a higher false positive rate for a urinary tract infection. Additionally, if for some reason
the child does get a spinal tap, most do not, a sterile CSF pleocytosis is possible just like
the sterile pyuria. Another key finding is low serum albumin. They often have that as well.
So, an echocardiogram is the main stain of watching for these changes in their coronary arteries.
We’re looking for coronary artery aneurysms. The echo may be positive early but usually,
the coronary artery aneurysms are a later finding. We obtain an echo around the time of diagnosis.
It’s not a huge emergency but we’d like to get it done in the first couple of days. The reason for that
is not only are we looking for some rare signs of involvement of the heart, patients can get myocardial
dysfunction or a pericarditis or they can get very mild dilatation or ectasia of their coronary arteries.
But mostly, we’re getting their early echo as a baseline for measurement of their coronary arteries
so that we can compare their coronary arteries later on when they come back for follow up visits.
We’re actually tracking for the development of an aneurysm. The management of Kawasaki
is something you should be very familiar with. After their five days of fever and once they’ve met criteria,
four or five criteria for the typical Kawasaki’s disease or two or three criteria with additional lab findings
and echo concerns, we will proceed to give IVIG. This is high dose IVIG which is 2 g/kg.
It’s given over many hours. It’s given slowly because IVIG has side effects we worry about.
An example would be shock. Patients getting IVIG can have significantly lower blood pressures
and go into shock. So, we’re going to administer it very slowly. Keep in mind there are some
side effects of the IVIG that should concern you. One of them is headache and that’s common.
But another concerning one is fever. This is because we’re using a resolution of fever of the disease
as a way of checking to see if the therapy is working. If they continue to have fever, we will wait
typically a period of about 36 hours after the IVIG is completed to check for fever because an earlier
fever may just be from the IVIG itself. Additionally, we will give aspirin. We’ll give high dose aspirin
while they’re in the hospital and in a febrile state. Then once they’re defervesced and ready
to go home, we will transition them to low-dose aspirin. The aspirin is given early as an anti-inflammatory
and later as a way to prevent clots forming in the event that child does form a coronary artery aneurysm.
There is some evidence that the aspirin is of little benefit. However, it’s very unlikely this is going to change
in the future because to do a study where you withheld aspirin would be hard to pull off.
Next, we will check these patients recurrently over a two to six week period, every two to six weeks
to make sure they are no longer having any involvement of their coronary arteries,
or that they’re having not at all, or that if there is involvement, we’re tracking that involvement.
These children will get routine follow up echos until cleared by the cardiologist.
So, that’s my review of Kawasaki’s disease. Thanks for your time.