Thread by @DrStevenTChen

SWEET SYNDROME - a #tweetorial/#medthread!

Join me for a discussion of this confusing eruption that we more commonly see on the inpatient side.

Bonus: a discussion on pathergy versus koebner phenomenon!

#MedEd #FOAMEd #dermtwitter #medtwitter #dermatology pc: @dermnetnz
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It helps to start by using the other name for Sweet Syndrome: Acute Febrile Neutrophilic Dermatosis. This pretty much sums up the whole syndrome.

Relatively sudden onset? ✅
Fever? ✅
Skin stuff? ✅

But what makes this diagnosis confusing is the differential diagnosis!
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If a patient presents with a fever + rash, we often start to consider infectious processes first, which is totally reasonable. What helps though, is the exam.

The rash in Sweet Syndrome is usually described as "juicy edematous papules and plaques."
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Since it's a neutrophilic dermatosis, that means that the infiltrate is full of PMNs in the dermis. So when early, it's a dermal process, and epidermal change is minimal.

But, with time, the PMNs aggregate & make pustules and can ulcerate, which can lead to secondary crust.👇
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Because of the differential diagnosis, often a biopsy is taken to make sure we're not dealing with an infection. It's hard to rule out infection on just pathology, so we'll take a tissue culture along with it to be safe.
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Since it's a neutrophilic dermatosis, PATHERGY is a hallmark of this disease.

What is pathergy you ask? Well, it's when dermal injury gives rise to a pustular lesion that can eventually ulcerate.

So quick test: which of the following DOESN'T pathergize?
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Since psoriasis is the only one that's NOT a neutrophilic dermatosis, it's the only one that doesn't pathergize. Instead, it does something called KOEBNERIZE. That's where epidermal injury makes the underlying rash happen more.

I made a slide in hopes it helps!
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Of note, there's a dx criteria for Sweet Syndrome, but I find that clinical impression usually trumps the actual criteria. You'll see that part of the criteria includes a bx and response to treatment, so not the easiest to use when you first see the patient! Thx @grepmeded
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So what actually causes Sweet Syndrome? Long story short, the actual pathophysiology isn't completely clear. We know of definite associations, like leukemia, neupogen, recent illnesses, etc. Problem is that there are a ton of case reports linking it to possible triggers.
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If I may share the most typical type of Sweet patient we see on consults:

50s-60s yo with AML s/p recent 7+3 now neutropenic, with new rash & fever.

The consult question is usually - "What is this rash? We know it's not Sweet because they're neutropenic!"

What do you say?
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A is correct! Points I'm trying to make in this scenario:

👉AML is the most common associated cancer. Sweet can be paraneoplastic.
👉You can still get it when you're neutropenic!
👉Patient's like this can be scary. It could be infection (& they should be treated for F+N!)
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Ultimately, when the stakes are this high, my threshold for biopsy is very low. I want to make sure I don't miss a disseminated infection (eg: fungal), or possibly leukemia cutis.

Just remember that the biopsy can cause the lesion to worsen and ulcerate, because, pathergy.
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The tx for Sweet is usually systemic steroids. If the trigger's removed, it shouldn't recur! There are some patients who get idiopathic Sweet, then steroid sparing agents are used. Those patients should probably undergo a workup to try to find a trigger (esp to r/o cancer!).
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Key points:
👉Sweet is a neutrophilic dermatosis, and as such, pathergizes when there's trauma.
👉Although it has characteristic findings on exam, if the patient is sick enough, a biopsy may still be warranted.
👉Dx is clinical (but there's a criteria). Tx is with steroids.
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I hope this #tweetorial of Sweet Syndrome was helpful! Now you know what #dermatologists are saying when we describe something as "juicy!"😂 Thanks for joining me! Until next time!
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