Here we have a really hot topic, called Hypersensitivity
pneumonitis. Clinically called Extrinsic allergic
alveolitis. Now, lets go down here for
one second, make sure that you are fully
aware of what’s going on. And by that
I mean, we had a discussion with occupational
lung diseases where we looked at pneumoconiosis
and in those, or in that discussion, we looked
at asbestosis, we looked at silicosis, we
looked at berylliosis and we looked at coalworker
pneumoconiosis, didn’t we?
Leave that behind and what we have here is
a patient who, once again, is'nt occupation,
but in this occupation, does not develop pneumoconiosis.
Does not necessarily develop all the things that
we talked about earlier, but ends up developing
a “allergic type of issue” and inflammatory
process. Now this is a group of mixed
disorder. There’s a lot of research going
on in terms of what exactly is the pathogenesis.
And the one thing that I wish to keep very
clear here is that you do not find
necessarily an abundance of eosinophilia.
Really? Yeah, you really don't.
So, at some point, when we jump into our discussion
of eosinophilic pneumonia, hypersensitivity
pneumonitis is really not going to be part
of that. Fascinating. So you want to be really
careful as to how you use the word hypersensitivity
and see as to whether or not... well, your
patient got exposed to something, is now having
a reaction and maybe a type III/type IV hypersensitivity.
Type III, immune complex and type IV, your
delayed type of hypersensitivity to environmental
antigens resulting in dyspnoea, cough, chest
tightness and headache. Okay. So, there will
be… the cough, would be more or less your
dry kind of cough, dyspnoea, interstitium is
being involved. There will be chest tightness
And by environmental antigens, we’re gonna
take a look at the list and this list, as
we go from coast to coast in the United States,
there are a lot of jobs that people have of
all different types and some of these jobs
may include working on the field, working
with different types of growth in agriculture.
So, our most researched and the most focused
group here that we know much about or that
we’re learning to deal, manage these patients
are farmers. And that’s where your focus
should be here as well. What did the farmer
then get exposed to that resulted in Extrinsic
allergic alveolitis? Lets continue.
Now the antibodies target specific antigens.
So, here is the antigen, environmentally,
a protein and even birds. Even pigeons.
Be careful. If you are given a scenario where
your patient is responsible for, well, we
call them bird fancier, and basically that
means that you have an individual that’s
growing birds. Or, while they’re growing
birds though, you think about maybe in their
garage, a very closed environment. Oh, mighty
stinky. So you walk in here, it smells bad
and it’s not that you’re breathing in
Cryptococcus neoformans, resulting in a type
of systemic fungal pneumonia. Be careful.
It’s a fact that, well, if you’re growing
these birds on a regular basis that you might
then be exposed to the proteins in the wings
or the proteins from the excreta. The proteins,
resulting in hypersensitivity pneumonitis.
Antibodies target specific antigens and approximately
two-thirds of your patients of hypersensitivity
pneumonitis develop a non-caseating granuloma.
Yet another example of non-caseating. You
know about sarcoidosis, you know about Crohn’s
disease, Berylliosis to a certain extent and
then here, hypersensitivity. This is an interstitial
pneumonitis. So therefore what do you think
you might have? Increased fibrosis.
And as soon as you have fibrosis that’s
taking place around the bronchioles, what
may this result in? Once again, bronchiolitis
obliterans. You see as to how, that is just
a very generic term or description, but it
tells you a lot as to what’s actually taking
place, what exactly is causing the fibrosis
in your patient to then obliterate the bronchioles.
Okay. As I told you earlier, it will be the
farmer that you’re going to be paying
attention to. Is that the only patient? No,
but the farmer is going to appear many times
on this table because that’s the focus group
for the most part, in which a patient
then comes in with maybe fever, headache and
chest tightness and coughing. Okay.
So, if it’s the “farmer’s lung”, exposure
to what? Mouldy hay. And imagine, there is
rain that has been, you know, going on for
a week and even in the next week, if it’s
been sunny, you can only imagine that the
hay and as to how it is then mouldy. And then
now the patient has been exposed to Thermophilic
actinomycetes. How does it behave? Behaves
as a hypersensitivity pneumonitis. This isn’t
actinomycosis where you end up having those
yellow-gold and sulphur granules around
the teeth and then may even have
a cervicofacial type of fissure. That’s
not what this is. Be careful. Even though
it seems like it’s the same bacteria, it’s
the particles of proteins.
What else? We talked about the bird fancier.
These individuals are growing different types
of birds, maybe perhaps even pigeons. But,
look at the antigen that you’ve been exposed
to. Proteins and organic dust from the bird
feathers or excreta, not to be confused with
Cryptococcus neoformans, which will then be
your, well, your caseating type
of granuloma, the type of pneumonia that you’re
probably very, very familiar with. Be careful.
Next. Byssinosis. So this is the textile
industry. So throughout the entire week,
the patient now has been working with cotton,
linen, hemp fibres in which throughout
the entire week, he or she is breathing this
in and resulting in that chest tightness,
headache, not feeling that great. Comes
home on a Friday and tells your, you know,
tells your loved one, “Listen, I am not
feeling that great, I don’t feel like going
out. Can we just stay at home and do whatever?”
And then, you see what I’m saying? Hypersensitivity
We have others, silo filler’s. You’re
working in a silo, filling stuff up. What
are you exposed to here in a silo? Fermentation,
nitrogen dioxide. How is your patient going
to present again? Cough. Number 2, it will
be dry in nature, interstitium. Number 2,
chest tightness and the most important thing
here is the history of your patient been exposed
to whatever antigen that was.
Then guess what your next step in management
is in all of these cases? Remove the patient
from the environment to see as to whether or
not the patient is going to be relieved. That’s
your next step of management. We’ll talk
more about that coming up.
Nylon flocker’s. So, those are that are
working with nylon. Proteins from nylon is
a big deal.
And say that you’re working with sugar cane.
This is bagassosis. So, bagassosis would be,
if you’re working with sugar cane, then
here, once again, been exposed to Thermophilic
Now in general, you can see, this is quite
non-specific and vague in terms of symptoms.
It’s not thoroughly understood, but it’s
understood just enough where we know that
it occurs and the list, ladies and gentlemen,
clinically, I have given you the most common
type of exposures, but it goes by hundreds.
Really. I mean, think about all the different
things that you might be exposed to.
Now definition. Here, it is important that
you pay attention. Extrinsic allergic alveolitis.
How would you diagnose your patient with hypersensitivity
pneumonitis? Now, we’ll walk through the
criteria. So, what we’ll do is, I’m going
to give you the criteria listed below and
then if it’s criteria 1, 2 and 3 that are
met and that’s the one that I want you to
focus upon, then your patient has Hypersensitivity
pneumonitis. The others, well, there’s a
combination of others and I’m just gonna…
There it is, take a look at it, but you pay
attention to 1, 2 and 3.
Number 1, I told you, history.
As the patient been exposed to whatever
antigen in that environment, a farmer, whether
from a silo, was it from birds, so forth.
Compatible clinical, radiographic and physiologic
findings, what does that mean? On chest X-ray,
if it’s the interstitium that’s been affected,
please understand that it will be reticular
pattern. Respiratory, well, your constitutional
symptoms there would be your fever, the
cough, the chest tightness that we talked
about, the crackles, worsening after several
hours after exposure. That is criteria number
Criteria number 2. It is not the eosinophilia
that you’re looking for. Is that clear?
So even though we call this hypersensitivity
and we even call this allergic, it doesn’t
necessarily mean that you have increased eosinophils.
So what you’re looking for in a BAL, stands
for bronchoalveolar lavage. In the lavage,
you end up finding lymphocytes of a low CD4
to CD8 ratio. So, who are you… Which one
of these lymphocytes do you have more of?
Good. It’s a CD8. Low CD4 to CD8 ratio.
Criteria number 2. Important.
Then criteria number 3. Positive inhalation
challenge test. Sure, meaning to say that,
now, the patient has been exposed to that
particular antigen and i’ll show you a graph
upcoming where it will show you that the symptoms
of your patient is going to worsen.
If criteria 1, 2 and 3 have been met, then
your patient has hypersensitivity pneumonitis.
Your first clue that your patient even has
such a pathogenesis or clinical picture
is, number 1, exposure to that antigen, and
number 2, the fever, the dyspnoea, the respiratory
issues and so forth.
Lets take a look at the graph here and
dissect it with hypersensitivity. And what
this is, and what it’s going
to show you is the fact that
you’ll notice that upon exposure, either
to the environment in the natural habitat
of your patient or, number two, you’re doing
an antigen type of test that hours later,
that you’re going to find worsening
of the patient’s condition. On the X-axis
represents the time in hours and the Y-axis
represents the percentage change from normal
to deteriorating type of condition. The blue
curve represents the environmental challenge
and the antigen is in the red curve.
Okay. So now, I told you, the first criteria
is to see as to whether or not the patient…
upon removing the patient from their environment,
are they going to feel better? Well, if from
the history you keep getting that the patient
says, “Hey, doc, every time I walk in that
silo, ooh, hours later, I don’t feel very
well, and then I leave and then
I go, you know, take a hot bath or whatever.”
And imagine that, actually that hot bath itself
could be, you know, another form of hypersensitivity,
but anyhow. They are not gonna give you two
scenarios at the same time. “I feel better
when I remove myself from the environment.”
You get that type of history every single
time, that’s your environmental challenge.
Antigenic challenge is the fact that you are
now, you have to be very careful here though.
Because if you are going to provide the antigen
which is then going to make the patient
feel not very good, do you understand to as
to how that’s, you know what I mean? Like,
exercise caution, make sure that you’re
always properly equipped with any type of
supportive therapy, just in case, the worst
case scenario. But this is just to illustrate
the importance of hypersensitivity pneumonitis
and its importance in terms of exposure.
Once again, would you tell me as to what that
second criteria was? Good. It was low a CD4
to CD8 ratio when dealing with the bronchoalveolar