So, first up, seborrheic dermatitis.
Now, this is also known as
cradle cap in infants, but it's important
to know that it can also
cause disease in adults. I'm
hoping that that's not a picture of our
female 18-year-old English major.
But either way, we do know that
seborrheic dermatitis is a chronic,
relapsing, mild dermatitis. Doesn't really
have any systemic manifestations or cause
particular trouble down the road. The
etiology is actually unknown, though
strangely, it is associated with
malassezia, which is a type of
fungus, and it does respond, oftentimes, to an
topical azole, you know, like ketoconazole,
that kind of thing.
So, still unusual exactly what the
pathogenesis is. As I said, infants, adults,
the only time where it can really
problems is in an HIV positive
patient. Has a predilection
for a number of different sites. Can
cause problems on the scalp,
behind the ears, the eyebrows,
the nasolabial folds,
the upper chest, the back, the
ears, lots of issues with
the eyelids, so called blepharitis,
and rarely even
can manifest in the axilla. And
importantly, the extremities are
spared. You're not going to
see this kind of itchy
lesions, eczematous lesions in the
antecubital fossa or down
the volar surface of the wrist, as we
might be seeing in our patient.
Is it pruritic? Yes, but pretty mild,
not intensely pruritic.
Shown here again, in our picture is
this scaly, flaky, so-called
greasy-looking plaques. That's the
term that should jump off the
page at you when you're reading it
in a board question.
Treatment, as I said, selenium
sulfide which has some
antifungal properties, and of course,
an azole shampoo like
that kind of thing.
Next up, let's talk about allergic and
irritant contact dermatitis.
First off, allergic contact dermatitis.
This is a localized
immune-response to a topical antigen, the
most common of which is something like
poison ivy. The urushiol, which
is an oil resin in
poison ivy and poison oak, that sort of
thing. It's T cell-mediated.
It's a delayed-type hypersensitivity reaction.
Doesn't immediately cause skin findings.
It's more delayed over a couple of days.
Acutely though, after a couple days,
you'll see these erythematous plaques
that will evolve into vesicles,
and as we're seeing in this patient,
may eventually lead to bullae.
Over time, if you're constantly
exposed to this allergen,
you may develop erythematous, indurated,
that is, fullness of the skin and
scaly plaques over time.
The most common allergens hands
down, no pun intended,
it's urushiol, which is the oil that
we find in poison ivy,
poison sumac, and poison oak.
Interestingly, we know this is an
allergy-mediated process as
opposed to some sort of
intrinsically toxic component in urushiol
because about 50% of people
actually have no response
when exposed to urushiol. Other common
allergens include nickel,
cobalt, latex, some topical antimicrobials,
and the preservatives in a number of
different soaps, shampoos, and
fragrances. And that's why
it's such an important point to take
a very thorough history, a
detailed history of every possible
when you're talking to patients who
are presenting with this kind of picture.
Treatment, obviously, it's going
to be to remove the
avoidable or remove the offending agent.
You can use anti-histamines
to help with discomfort. Patients
really are very itchy with this
condition and they're asking for something
to help them and some anti-histamines
can be helpful. Occasionally,
we'll use topical
or even systemic steroids in
severe cases, or if
it involves the face or other
sorts of areas.
Now let's talk about irritant
Rather than being immune-mediated,
this is an acute or chronic,
local inflammatory reaction to a cytotoxic
stimulus, whether it's physical or chemical.
That substance is actually directly
causing a disruption of
the epidermal barrier with direct
injury to keratinocytes
or to the cell membranes. It is, for
whatever reason, more
common in women. There's this
association that historically or
traditionally, women were more social
professions involving cleaning
and using hand solvents, things like that.
So there has been an increased risk
of occupational exposures amongst women.
Common irritants, as I'm suggesting,
detergents, some surfactants,
alkali-based compounds, bleaching agents.
In a chemical plant, you may see this
happen with fiberglass exposure,
some dusts, plants, of course, some
types of toxic alcohols.
And in kids, simply a diaper dermatitis,
, the mixture of stool and urine and a moist
environment can cause this irritant
contact dermatitis as well.
Treatment, very similar.
Just remove or avoid the offending agent.
And we can still use those other things
like anti-histamines and
occasionally, steroids to help. So,
putting these 2 side by side,
contact dermatitis, it's a T cell-mediated
response to an allergen.
Considered a delayed type
and it can be acute or chronic. The irritant
type is a localized inflammatory
response to something that is
physically or chemically toxic.
And it's a direct cytotoxic response
that you're seeing.
This can also be either acute or
chronic. It depends on how
much of the agent you're being exposed
to over how long a span of time.
So, going back and thinking about our
patient, this is occurring on both
extremities in the antecubital fassa. It's clearly
symmetric So, is it possible that
she has been applying some lotion to
the area and the lotion itself is what's
precipitating the immune response,
therefore being an allergic contact dermatitis?
It's something to consider and it
would certainly be important to
talk to our patient
and inquire about what she's applied
to the area for her symptoms.
Now let's talk about psoriasis.
variety of different subtypes, the most
common of which is simply
plaque psoriasis. And this picture shows
both some plaque psoriasis
subtypes, as well as
in the bottom picture there, you can
see so called Palmo pustular
psoriasis with more of those
vesicles and pustules.
But typically, we're looking
for silvery scale.
That's the classic description you'll see
on the boards, is this silvery plaque
on an erythematous bed, and if you were
to scrape off one of those plaques,
you'd get this punctate bleeding that would
occur right underneath the plaque
And that's, again, it's one of those
that you would see with psoriasis.
So, let's go back and revisit the case and
see if any particular points about
atopic dermatitis jump out at us. So,
again, our 18-year-old English major had a
history of "dermatitis." Who knows exactly what
that means to this particular patient? But
we do know that atopic dermatitis is
more common in children, far
more so than in adults.
The vast majority will have symptoms
before the age of 5.
So if you have a patient coming in
with a new dermatitis, and they're
in their 20s, or 30s, atopic dermatitis
would be much less likely
to be the cause.
In fact, atopic dermatitis, most commonly,
gradually remits with age, such that
those children who had atopic
dermatitis before the age of 5, only about 5%
will still have symptoms by the time
they're 20 years of age or older.
And that's similar to the, sort of, natural
history for childhood asthma.
Next up, the types of features that will
be relevant to make us thinking about
atopic dermatitis. We see here that
in the social history, our patient had a
mother with asthma, a brother
who's allergic to "everything."
And then looking above that in the HPI,
our patient has a history of allergic
rhinitis, mild asthma, seasonal allergies.
These are all bells that should be
ringing saying, "Family history and
personal history of atopy."
Importantly, the cause of
atopic asthma is really
still unknown. All we know is
that it is some sort of
immune-mediated process, but
exactly what triggers it is
not clear. It's possible that it's a
problem with skin barrier
dysfunction and that certain
external antigens are
penetrating the skin and triggering
immune cells in the skin
to become inflamed and to release certain
cytokines into the skin. There may be
simultaneously some immune dysregulation,
or may just be some cutaneous
to normal environmental stimuli.
And lastly, on this page, when we
think about the physical exam,
these are the classic features that
you should be looking for, and
these things really make the clinical
diagnosis. You shouldn't need a biopsy.
Dry, lichenified, erythematous plaques,
with possibly some scattered papules, lots
of excoriations from all that scratching.
And the most common places are going
to be the antecubital fossa, perhaps the
volar aspect of the wrist, the flexural
creases behind the legs.
Those are the types of areas you
should be thinking about.
If you were to do any blood testing
and largely unnecessary, but
IgE levels would likely be elevated.
And you could do specific
skin prick testing
to see if there's any particular allergens
that trigger atopic
eczema in this particular patient.