Alright, we're gonna cover a big topic
today, virally mediated skin lesions.
Let's get started, as we always do, with a case.
An 11 year old healthy girl presents with a rash.
Her mother states that she's noticed a crop of
round bumps appearing on her trunk and her thighs
over the past several days and particularly
in the groin and in her armpits.
The mother appears more distressed
about them than the daughter,
who reports that they aren't bothering her at all.
Patient denies any fevers, chills, myalgias,
arthralgias, URI symptoms or GI symptoms.
The only thing is that some of
the lesions are very mildly itchy.
Social and family history - non contributory.
Review of systems as we've discussed is totally
negative and her vital signs are completely normal.
What we see on exam is numerous subcentimeter, skin
colored, dome-shaped papules scattered on her torso
and we can see some here on the picture on the right.
They're also in the axillae,
the crural folds, the proximal thighs.
The lesions are very shiny in appearance, umbilicated, they're
non-tender and they're firm, sparing the palms and the soles.
And importantly, there's no
evidence of any mucosal lesions.
So, let's look at a few key points here,
highlighting some prominent variables.
Number 1, they sound acute.
They've just been coming on
over the past couple of days.
Secondly, the pattern of skin involvement,
they're located on her trunk, in her thighs
and rather asymmetrically distributed.
Skin inflammation, the fact that they're
non-tender, there are not any postules.
It doesn't sound like there's any skin inflammation
and there really is no evidence of any
skin involvement or systemic involvement
based on the comprehensive review of systems.
Alright, so let's take a look at our
differential diagnosis for this case.
First stop, keratoacanthoma.
Now, keratoacanthomas are indeed often
described as dome-shaped firm papules.
There's one right there and it
does kinda look like what she has.
And they'ren asymptomatic which
is also similar to what she has.
But they don't appear in crops
as they did in our patient.
They are isolated, individual lesions
with a central keratotic plug.
Moreover, you'd almost never see
one in an 11-year-old girl.
It's a disease of folks over the age of 50.
It represents a type of very low grade
malignancy, sometimes called a pseudocancer.
Now, in defense of it's appearance in this
section on viral diseases of the skin,
I would be remiss if I did not also mention
that it is strongly associated with HPV.
So, it's a reasonable thing to have in this topic, but
it's definitely not what she has, so let's X it out.
Next stop, varicella, also known as chickenpox.
Well, it's one of the many viruses that can cause a
so-called viral exanthem, dozen of viruses can do this.
Now, the lesions of chickenpox can come on fairly
quickly, just like our patient did, over several days.
And they might indeed look like
round, dome-shaped lesions.
But the lesions of chicken pox are actually
fluid-filled vesicles rather than these firm papules.
And varicella, like most viral
exanthems is accompanied by symptoms:
Fevers, malaise, myalgias, headaches,
perhaps even a sore throat.
I had it when I was 19, it was terrible.
Now less commonly, viral exanthems could have diarrhea,
lymphadenopathy, maybe even splenomegaly or hepatomegaly,
Either way, it doesn't sound like what she's got.
Varicella lesions often transition from vesicles to
pustules after a few days and ultimately will cross over
and resolve spontaneously in less than 10 days.
Just rounding out the discussion about varicella.
So, I think we can safely take
it off of our list for now.
Now, this rash which is also caused by a virus, the molluscum
contagiosum virus is relatively common in children.
The lesions of molluscum contagiosum
are described as dome-shaped papules,
randomly distributed on the torso and
extremities in an asymptomatic host.
Looks like we'll need to keep
this one on the list for now.
Those lesions do look familiar.
Next stop, measles.
Okay, this is yet another virus that
causes a viral exanthem and like varicella,
it's typically accompanied by a viral prodrome.
Fevers, malaise, cough,
conjunctivitis is common and sinus congestion.
Now, the lesions themselves are typically
diffuse, erythematous maculopapules,
often referred to as 'morbilliform' because
many other viruses look the same as measles.
They're only a few millimeters in size, shown here in the
top right picture and they typically start on the face,
spreading caudally with areas of
confluence often on the chest and the neck.
Shown here on the bottom right is a reminder that
measles is also associated with classic mucosal lesions
called 'Koplik spots', you'll definitely
see this referenced on the boards.
They are grayish, white, flat macules on an erythematous base,
seen on the buccal mucosa adjacent to the molars as shown here.
Now, our patient had firm, dome-shaped papules.
No mucosal lesions, not to mention
she was completely asymptomatic.
So I think we can definitely
take this one off of our list.
Lastly, let's talk about erythema multiforme.
Remember, while we often think of erythema
multiforme along with Steven-Johnsons Syndrome and
toxic epidermal necrolysis
associated with drug reactions,
keep in mind that 90% of erythema multiforme
eruptions are actually due to infections,
most notably HSV and then
mycoplasma would be second in place.
Let's take a look at the next slide to review
erythema multiforme in some more detail.
So, here's some picture shown in the right of
classic erythema multiforme manifestations.
It is an acute, immune-mediated eruption
with targetoid-shaped lesions depicted here.
It's really gonna afflict young adults,
predominantly under age 30, oftentimes, under age 10.
90% of them as I mentioned are caused
by infections like HSV and mycoplasma.
Less than 10% of the time, it's caused by drugs.
As we'll see in some other lecture talking
about SJS and toxic epidermal necrolysis
that ratio is flipped with a small number causing, or caused
by infections and a much larger number caused by medications.
What you'll see here on the right are
these targetoid erythematous papules
that are symmetrically distributedon the hands and
the face with a centripetal spread towards the torso.
And you can note here the central
clearing on some of those lesions.
As a quick aside, sometimes I have trouble remembering
what centripetal versus cetrifugal means.
Always remember cetrifugal has F-U-G,
and that makes me think of a fugitive.
What are fugitives doing?
they're running away.
So centrifugal means striding away from the body as
opposed to centripetal is running towards the body.
or coming towards the body.
Important for us to remember that there
are two subtypes of erythema multiforme:
the minor and the major subtype.
The minor subtype is basically
characterized by just the rash alone,
whereas the major subtype is more like a
Steven-Johnsons syndrome type of picture
with mucosal involvement, malaise, myalgias,
fevers, other constitutional symptoms
and it's much more significant of course.
Our patient, clearly, if anything would
be looking like a minor variant here.
The way that it's managed, if it's mediatied or caused
by herpes simplex virus, you're gonna want to treat that.
Withdraw whatever culprit medications could be playing a
role and you may need to add on systemic glucocorticoids,
generally just for the major
subtype of erythema multiforme.
So, having reviewed erythema multiforme, I
think we can safely take it off our list
as the lesions are wholly inconsistent with our
patient's dome-shaped, skin-colored papules.
Alright, so it looks like we're
left with molluscum cotagiosum.
So let's revisit the case and
highlight some key points.
Alright, so molluscum contagiosum is very
common in children and the immunocompromised
and our 11-year-old healthy girl would be a perfect
case of somebody getting molluscum contagiosum.
The lesions here, the round bumps appearing on
her trunk and thighs over the past several days
particularly the groin and the armpits,
this is a classic presentation as well.
Molluscum contagiosum lesions are asymmetric,
they've predilection for flexural creases
and they spare the palms, the soles and there
should not be any mucosal involvement.
Next stop, as we've highlighted countless times over
the past few minutes, patients should be asymptomatic.
They shouldn't be manifesting with the classic viral
syndrome of myalgias and fevers that sort of thing.
Next stop, the lesions as we've said are dome-shaped
papules with these characterized central umblication,
a little bit of a hallowing out in the
center of the lesion and they're non-tender.