Thread by @DrStevenTChen

It's #tweetorial time! Read on for a #medthread on:

Cutaneous Small Vessel #vasculitis (CSVV)!

#MedEd #FOAMEd #dermtwitter #dermatology #medtwitter #rheumtwitter pc: @dermnetnz
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I've heard different ways to organize the vasculitides over the years, but by the far the most common is by vessel size. As a #dermatologist, I see the small vessel vasculitides most often, so we'll focus on that today. Yes, Takayasu's important, but I'll save that for later!
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There is a relatively limited list of possible diagnoses with CSVV. I've included the most common below.

The blue I lump together as they are similar, and biopsy results help you differentiate.
The red are the ANCA-associated.
The green are the unique ones.
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The nice thing is that most of the list present with similar exam findings. The green diagnoses (EED and UV) are different, which we'll discuss later. However, most present with palpable purpura! This can be subtle, so even if it's macular but purpuric, still consider CSVV!
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Remember that given the compromise in the vasculature, areas can appear retiform. Also, because of the interruption in blood flow, the skin can ulcerate, so old lesions may open up! Remember this tweetorial that explains why this happens? 👇👇👇

https://twitter.com/DrStevenTChen/status/1099828893656252416

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Erythema elevatum diutinum (EED) & Urticarial vasculitis (UV) look different. EED (photo 1) shows papules and nodules. This is really rare!

Urticarial vasculitis (UV) looks like hives (photo 2). Both show a "leukocytoclastic vasculitis" (LCV) on biopsy - more on that later.
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The 3 Ps can help distinguish UV from urticaria - Pain (burning), Persistence (>24 hours), & Pigmentation (leaves post-inflammatory hyperpigmentation, as shown in the photo). If you suspect UV, a biopsy is diagnostic, and we'll send some tests. What should we send?
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We will usually send complements after a diagnosis of UV since hypocomplementemic UV has been associated with lupus. That said, a quick pubmed search reveals that since this was first reported over 40 years ago, there have been many other associated connective tissue diseases.
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Let's go back to discuss the other types of CSVV. Essentially, after an exam reveals palpable purpura, the work up begins. Before sending off A TON of tests, I'd advocate for a good H/P first! That should really drive the decision to pursue testing (and helps save money!!)!
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If the pt developed the vasculitis while in house, I'd argue it's probably from something we gave! A good drug chart might reveal a trigger for this new rash. If the patient had a recent URI, that might be the reason! In these cases, supportive care might be all you need.
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However, if you can't identify a potential trigger, & a more broad work up is necessary, tailoring it to your patient makes sense too. Lung disease, nasal polyps, history of asthma? Send ANCAs! Belly pain & arthralgia? Maybe it's HSP! This is where a skin bx can be helpful.
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As you might expect, EGPA, GPA may show granulomas on bx. Leukocytoclastic vasculitis (pic) basically shows what the name implies: neutrophils falling apart and causing inflammation in the vessels. HSP and IgA vasculitis are similar to LCV, but with IgA on immunofluorescence.
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So what's the difference then between HSP and IgA vasculitis? I've heard some people call all IgA vasculitides HSP, but I've also heard some differentiate between them. Some only call it HSP if the patient has sxs like belly or joint pain. That said, tx is usually similar.
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In #pediatrics, HSP is often 2/2 strep throat, a recent URI, or other illness. However, in adults, I think more about drug triggers and possible paraneoplastic processes. Since the kidneys can be involved, I will check a UA, and do so periodically for some time after dx!
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Importantly, if a DIF is sent too late, you can get a false negative. For that reason, even without IgA on the DIF, I still consider triggers, and still will monitor UA as above.

This article quotes 7 days, but I've learned to do DIF within 2-3 days!
ncbi.nlm.nih.gov/pmc/articles/P…
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As mentioned above, if I can't figure out a trigger, I'm continuing the work up. This might include cryos, RF, hep serologies, SPEP, cultures, etc. The exact workup varies for me depending on the H&P, whereas some will send everything on 1st pass. I like a stepwise approach.
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Let's talk tx. If there is renal involvement, or if we're dealing with a more systemic vasculitis, you can bet I'm calling my #rheumatology colleagues! If, however, it looks to be both self and skin limited, I'll start with class 1 topical steroids.

https://twitter.com/DrStevenTChen/status/1123605778127052800

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But if the patient has large areas of skin with impending necrosis, I may reach for systemic steroids in hopes of avoiding ulceration. Once the skin is ulcerated it takes weeks-months to heal, so preventing that is critical. I transition to steroid sparing agents when able!
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RECAP:
- most CSVV p/w palpable purpura
- use H/P to direct work up (my opinion)
- bx +/- DIF can help

For LCV
- if skin/self limited, topical steroids, with monitoring of UA
- use systemic agents to avoid ulceration if possible
- inpatients with new LCV may be 2/2 drug
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This topic was a bit more complicated to present in #tweetorial format, so apologies if it was a bit convoluted. Happy to take suggestions or if you'd like to add any information here (looking at you #dermtwitter #rheumtwitter & #dermatopathology folks)!

Hope this helped!
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