The rash of livedo reticularis (LR) is characterized by erythematous to purple rings with central clear areas of normal skin. The underlying etiology appears to be alteration of blood flow and resultant lowered oxygen tension in the skin. The most common location is the lower legs, but the trunk and arms may be affected as well. LR is usually asymptomatic, but the patient may on occasion complain of coldness, numbness, paresthesia, or aching. The rash is often more prominent when the skin is cool. Warming the skin may reduce the rash's prominence, but the reticulated pattern persists.
Some authors distinguish LR from livedo racemosa. Livedo racemosa may be defined as an incomplete netlike pattern in larger circles rather than the smaller, complete retiform pattern seen with LR. We believe the entities are very closely related if not the same and do not usually distinguish between the two on a clinical basis.
The majority of patients with LR have no underlying pathology, but because the condition may signal significant underlying systemic disease, a thorough workup is required to reach that decision. Broad categories of underlying diseases include a host of hypercoagulable states, connective tissue disease, vasculitis, deposition of either emboli or other substances in the vessel walls, medications, infections, neoplasia, neurologic disease, endocrine disease, and a few other unclassified conditions. A detailed list of underlying diseases has been compiled by Gibbs et al.
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The differential diagnosis of LR includes leukocytoclastic vasculitis, cutis marmorata, erythema ab igne, viral rashes, and reticulated erythematous mucinosis. The most important entity to distinguish is leukocytoclastic vasculitis because it can include systemic involvement with renal damage. Also commonly referred to as palpable purpura, leukocytoclastic vasculitis has a raised or papular component, whereas LR is flat. Moreover, leukocytoclastic vasculitis does not form the characteristic ringlike pattern of LR.
Cutis marmorata, a common mimic of LR, is seen most often on the extremities of children or women as a similar pattern of ringlike patches, often with a bluish hue. However, in contrast to LR, these disappear on warming the affected skin. Erythema ab igne is a curious dermatosis seen in those who habitually use heating pads or hot-water bottles, resulting in a persistent, localized netlike dark red to hyperpigmented pattern most often on the lower back. Reticulated erythematous mucinosis is seen usually in young females as erythematous netlike plaques on the anterior chest or upper back. The histology is very similar to that of tumid lupus erythematosus; in fact, the two may be one and the same. A localized condition, erythematous mucinosis has a raised component due to mucin deposition in the dermis and is more erythematous than most cases of livedo.
The history and physical examination of a patient presenting with LR should include queries about symptoms related to connective tissue disease, personal or family history of thrombosis, new neurologic findings, risk factors for hepatitis C virus (HCV), renal failure, and medication history. Laboratory evaluation is directed by the history and physical but should include a lupus anticoagulant panel in nearly all patients with livedo not exclusively and clearly related to cold exposure.
One hypercoagulable state associated with LR is cryoglobulinemia. Cryoglobulins precipitate in cooler temperatures and plug small vessels in the skin. These immune globulins are not uncommon in HCV infection. Dusky plaques may also be seen in acral regions in patients with cryoglobulinemia.
Our patient's LR was attributed to his known HCV infection. No specific therapy was indicated or initiated due to the asymptomatic and relatively benign nature of his condition.
Dr. Krathen is a dermatologist in private practice in Palm Beach, Fla., and Dr. Hsu is professor of dermatology at Baylor College of Medicine in Houston.
Reference
1. Gibbs MB, English JC, Zirwas MJ. Livedo reticularis: an update. J Am Acad Dermatol. 2005;52:1009-1019.