Livedo reticularis and livedo racemosa

We’ve had a purple, net-like week here at ZSFG. At both M&M and intern report we talked about livedo rashes. After both conferences, I was still confused. So I looked it up in a dermatology textbook. Here’s what I learned.
Top pearls
  • Livedo reticularis can be primary and benign or secondary and very bad
  • Livedo racemosa is morphologically different and always bad
  • There’s a lot of conflicting information out there about the distinction between these two conditions!
Pathophysiology of livedo rashes
  • both racemosa and reticularis arise from deoxygenation or dilation of the venous plexus in the skin
  • veno-dilation can be benign (due to cold, called cutis marmorata) or from one of the following pathologic processes
    • small vessel sludging/clotting (due to coagulopathy)
    • vasospasm
    • vasculopathy
Livedo reticularis
  • the rash of classic Livedo reticularis  is “fishnet-like, red or purple mottling [that] surrounds a pallorous conical core.” The rings are closed/complete circles and relatively symmetric
  • Here’s a good picture from the mayo clinic. The circles can definitely bigger/more netlike.
Livedo racemosa
The rash of livedo racemosa is the same color, but tends to be more broken and asymmetric. It partially goes away with warming, but not completely.
Screen Shot 2017-02-17 at 10.59.24 AM.png
  • Livedo reticularis can be primary or secondary. 
    • primary is caused by cold or is idiopathic and requires no special management other than cold avoidance.
  • Livedo Racemosa is always secondary and bad.
    • Always, always test patients with racemosa for APLS.
  • The DDX for secondary reticularis and racemes is super broad, and can be categorized using the clotting, vasospasm, vasculopathy framework above. See a full differential below.
Let me know if you have a different framework for thinking about these! Every paper had a different definition and very strong opinions =)
Chadachan V, Dean SM, Eberhardt RT. Chapter 173. Cutaneous Changes in Peripheral Arterial Vascular Disease. In: Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ, Wolff K. eds. Fitzpatrick’s Dermatology in General Medicine, 8e New York, NY: McGraw-Hill; 2012. Accessed February 17, 2017.
Gunderson CG, Federman DG. Web of confusion Am J Med. 2011 Jun;124(6):501-4. (this is where the table comes from)

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