Voiceover: Henoch-Schonlein purpura is a
small vessel vasculitis.
First before, we go into detail, let's look
at what causes Henoch-Schonlein purpura.
Here, I'm going to draw a blood vessel wall,
and again blood vessels are just like pipes, so
it's like we're taking cross section down
the middle of a blood vessel.
So we are looking at the inside of
a blood vessel here and remember antibodies
are attaching to the vascular wall,
which recruit white blood cells because
these antibodies act like a marker, and
these white blood cells cause damage
to the blood vessel wall.
And these antibodies can group together,
and there is little proteins that they're
targeting and they latch on to.
And so these little proteins can be shared
between the antibodies. Remember these proteins
are called antigens because they generate
an antibody response, and a group of these
antibodies and antigens is called an immune complex.
Other small vessel vasculitides is antibodies
may be associated or may actually be ANCA,
antineutrophilic cytoplasmic antibodies.
But in Henoch-Schonlein purpura, ANCA is not found.
Instead what we see, are elevated levels of IgA.
IgA is a specific antibody that is found
on mucosal surfaces, so for example,
any part of your inside that's somewhat
exposed to the outside of your body.
Great example is the intestines like
I'm scribbling down right here.
Your gastrointestinal system goes from the
mouth all the way to the anus.
So the gastrointestinal tract covers the
distance between the mouth and the anus.
You can also see IgA in your lungs or
in your respiratory tract. Remember your
intestines and your respiratory tract are
exposed to the outside through your mouth.
So IgA is a way to prevent pathogens from
trying to enter inside of your body
through these mucosal or "wet" surfaces of your body.
Now, I want to highlight this because
Henoch-Schonlein purpura is associated with
upper respiratory infections. It's believed
that some sort of pathogen gets into the
respiratory tract causes an infection and then
causes release of these IgAs to combat the infection.
However, coincidentally these pathogens
that are causing an infection share similar
components that kind of look like
the wall of blood vessels. This similarity
is called molecular mimicry, and it's
believed that antibodies that are released
in response to an upper respiratory infection
also accidentally attach onto the blood
vessel walls in Henoch-Schonlein purpura.
And then you also see formation of these
immune complexes as well, so this case of
mistaken identity, this molecular mimicry
is really the cause of the disease process.
And so let's take a look at the symptoms that you see.
In Henoch-Schonlein purpura as we said
we have an elevated IgA, so that's actually
one blood test that you can use to look for
Henoch-Schonlein purpura because elevated levels
of IgA are normally not found in the blood, but also
you can find immune complexes, and
these immune complexes formed in the blood
travel down to joints and can cause
joint pain known as arthralgias.
This can happen in the elbows as well
and the shoulders too, really anywhere there is a joint.
And these IgA complexes, these immune complexes
also deposit in the kidney, and so
you can see some kidney damage and
bloody urine which is known as hematuria.
And these complexes also have an affinity
to get stuck in the intestines, and so you
may see bloody diarrhea, bloody stools,
which are known as melena, which is dark stools
or hematochezia, which is bright red
blood in the stools. You can also see
abdominal pain. Let me take a moment to
mention that you have little kids being
affected by this disease. This is the most
common vasculitis that affects children,
so you can see a kid with abdominal pain,
just screaming in pain and having all
this pain in their joints as well.
Added on top of that, they have bloody urine
and bloody stools. That's going to terrify parents.
But one of the classic symptoms of
Henoch-Schonlein purpura are skin lesions.
Most commonly on the buttocks, but also
commonly found on the leg as well.
These skin lesions are called purpura.
In fact, this is not any normal type of rash
or purpura, this can be felt as palpable.
Immune complexes are deposing in this area
causing damage to blood vessels that
are supplying the skin, which is causing
the death of skin cells. This rash is known
to be palpable. Palpable means you can touch it,
you can kind of feel the bumps if you run
your fingers over it. The reason it's palpable
is because of the swelling that's occurring
from the immune complex deposition.
So if you see these classic symptoms in a child,
it can also be a teen or even adults can be
affected by it, you need to treat with
steroids. Steroids inhibit the immune system
from causing further damage to blood vessels.
And with time, this disease should actually
go away. It's a very self-limiting process.
Remember it was caused by an infection of
the upper respiratory system so that would be the
trachea, the throat, so on and so forth.
And so once you treat, this illness should go away.