Livedo reticularis produces a mottled, purplish discoloration of the skin with reticulated cyanotic areas surrounding paler central cores. This distinctive “fishnet” pattern is caused by spasm or obstruction of perpendicular arterioles, combined with pooling of blood in surrounding venous plexuses. Idiopathic livedo reticularis is a benign condition that worsens with cold exposure, improves with warming, and primarily affects the extremities. Apart from cosmetic concerns, it is usually asymptomatic. The presence of systemic symptoms or the development of cutaneous ulcerations point to the presence of an underlying disease.
Secondary livedo reticularis, termed livedo racemosa, occurs in association with diseases that cause vascular obstruction or inflammation. Livedo racemosa resembles idiopathic livedo reticularis but has a wider skin distribution, including trunk, buttocks, and extremities. Its lesions are more irregular, broken, and circular. Of particular importance is the link with antiphospholipid antibody syndrome. Livedo racemosa is the presenting manifestation in 25% of patients with antiphospholipid antibody syndrome and is strongly associated with the subgroup that has arterial thromboses, including those with antiphospholipid antibody–positive Sneddon syndrome (livedo reticularis and cerebrovascular events). Other underlying causes of livedo racemosa include the vasculitides (particularly polyarteritis nodosa), cholesterol emboli syndrome, thrombocythemia, cryoglobulinemia, cold agglutinin disease, primary hyperoxaluria (due to vascular deposits of calcium oxalate), and disseminated intravascular coagulation.
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et al. Characteristics, risk factors and treatment reality in livedoid vasculopathy—a multicentre analysis. J Eur Acad Dermatol Venereol. 2019 Sep;33(9):1784–91.