Relatively sudden onset? ✅
Skin stuff? ✅
But what makes this diagnosis confusing is the differential diagnosis!
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?
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?
👉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!)
Just remember that the biopsy can cause the lesion to worsen and ulcerate, because, pathergy.
👉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.