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.
- 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)
- 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.
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.
- 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. http://accessmedicine.mhmedical.com/content.aspx?bookid=392§ionid=41138898. 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)