Livedo reticularis (LR) is a common vascular reaction pattern characterized by a reticular (net-like) discoloration on the extremities and trunk. It is caused by decreased blood flow to the skin or impaired outflow in the dermal venous plexus and stagnation of the blood within these vessels. The darker, discolored areas represent accumulation of deoxygenated blood. Etiologic categories include vasospasm, vessel wall dysfunction (eg, vasculitis), and vascular flow compromise as in coagulopathies.

LR is exacerbated by cold temperatures. It may be physiologic (cutis marmorata), a primary disease (as in idiopathic cases), or it may be secondary to underlying disorders such as antiphospholipid antibody syndrome, vasculopathies, or autoimmune connective tissue disorders. Amantadine, quinidine, and catecholamines have also been described as triggers. Drugs used in the past to treat syphilis (bismuth and arsphenamine) also caused LR. Furthermore, infections can induce LR via the formation of cryoglobulins, cold agglutinins, septic emboli, immune vasculitis, or septic vasculitis. In adults, LR is frequently seen in patients with Raynaud phenomenon, in those with a predisposition to chilblains and acrocyanosis, and in patients with poor vascular flow (eg, peripheral vascular disease and cardiac failure).

These secondary forms may also present with livedo racemosa, where the reticular pattern is asymmetric, discontinuous, and localized. Localized forms may be associated with vasculitis. In severe cases, the extremities are cold and ulcers may form.

Sneddon syndrome is extensive diffuse LR or livedo racemosa with cerebrovascular disease (from transient ischemic attacks to frank cerebrovascular accidents), hypertension, and antiphospholipid antibodies.