What causes livedo reticularis?
Livedo reticularis results from a disturbance of blood flow to the skin, causing low blood flow and reduced oxygen tension to the skin. Cutaneous vasculature is comprised of a series of 1–3 cm cones. The apex of each cone is located deep within the dermis at the site of an ascending arteriole. At the margin of each cone, the density of the arterial bed is decreased, and the superficial venous plexus is more prominent. Any pathological or physiological process which impairs blood flow to the skin results in higher amounts of deoxygenated haemoglobin, leading to a livid discolouration.
Physiological arteriolar vasospasm in response to cold, produces reversible skin discolouration, such as in cutis marmorata. Prolonged vasospasm, thrombosis or hyperviscosity can cause the pathological skin changes of livedo racemosa.
A unilateral form of livedo reticularis due to local heat injury is known as erythema ab igne.