Thread by @DrStevenTChen

It's been about a week, so I thought it'd be a good time for another #dermatology #tweetorial/#medthread! Let's talk about another derm emergency that really gets me worried for the patient: #purpura fulminans (PF)!

Thanks @dermnetnz
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#FOAMed #MedEd #dermtwitter #medtwitter

What is purpura fulminans? It's basically retiform purpura, EVERYWHERE! But what is retiform purpura? It's the sharp angulated purpuric plaque/patch you can see in the skin. When you see retiform purpura, it means there's likely either a vasculitis or vasculopathy causing it!

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Why does that happen? (Nerd-alert - this is one of my favorite ah-ha moments from residency) - The skin is perfused in cones, so if you knock them out, you get circles of necrosis. When you combine a bunch, you get the angular appearance! See my terrible MS paint attempt:

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Mortality rate after PF can be astronomically high, over 50% in some studies! DON'T FORGET - If we see PF, we can't stop there as it is merely a sign of the actual underlying disease process.

What do you think is the proposed pathophysiology of PF?
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The reason that I've seen floating around in literature is protein C/S deficiency leading to a prothombotic state. This might explain why you see PF for different reasons in different groups. Take a look at this article from some colleagues at #MGH:

…edirect-com.ezp-prod1.hul.harvard.edu/science/articl…

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In adults, infection is the usual cause for PF, and a consumptive process causing a transient low protein C/S state may be to blame. In #pediatrics, PF can occur in neonates with inherited C/S deficiencies! So when you see PF, think about what is causing a low Protein C/S!

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In adults, the most common infectious causes are encapsulated organism (such as capnocytophaga, meningococcus, S. pneumo, etc). As you might suspect, splenectomy is a risk factor for these infections - a good reminder to make sure our splenectomy patients are fully immunized!

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Remember though that other infections can cause it, including viral processes, and tick-borne illnesses. Catastrophic APLAS can also cause this!

As you mind imagine, broad spectrum antibiotics (and possibly doxycycline) is a good place to start for therapy.

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Other therapeutic options have to do with the pathophysiology. Some will give heparin, and some will give activated protein C.

This is a good time to mention that there are certainly other potential causes of PF. Basically anything that can cause DIC can cause PF.

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So how does a @dermhospitalist help? We know that PF is basically DIC in the skin, and DIC systemically is likely coming. As such, we usually recommend:

- Admission (consider the ICU)
- trend DIC labs
- pan-culture
- start antibiotics as above
- get those pressors ready!

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For the skin itself, it will start necrosing and lifting off. Not much to do but to leave it intact as a natural dressing, and to provide excellent wound care. Many patients also unfortunately end up throwing clots into major arteries, making gangrenous limbs a possibility.

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I will never forget the first case of purpura fulminans I ever saw. I was a resident on consults at #MGH, and was shocked by the rapid progression. The case was actually written up as a @NEJM CPC with some great teaching point.

nejm.org/doi/full/10.10…

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Thanks for reading! To recap:
- Purpura fulminans is DIC in the skin
- PF = badness is coming.
- Consider broad spectrum antibiotics, watch for DIC, and look for the cause.
- Leave the dead skin in place, and good wound care is key!

Hope this was helpful! Comments welcome!

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