Livedo reticularis is a common skin finding consisting of a mottled reticulated vascular pattern that appears as a lace-like purplish discoloration of the skin. The discoloration is caused by reduction in blood flow through the arterioles that supply the cutaneous capillaries, resulting in deoxygenated blood showing as blue discoloration. This can be a secondary effect of a condition that increases a person's risk of forming blood clots, including a wide array of pathological and nonpathological conditions. Examples include hyperlipidemia, microvascular hematological or anemia states, nutritional deficiencies, hyper- and autoimmune diseases, and drugs/toxins. The condition may be normal or related to more severe underlying pathology. Its differential diagnosis is broadly divided into possible blood diseases, autoimmune (rheumatologic) diseases, cardiovascular diseases, cancers, and endocrine disorders. It can usually (in 80% of cases) be diagnosed by biopsy. It may be aggravated by exposure to cold, and occurs most often in the lower extremities. The condition's name derives from the Latin livere which means bluish, and reticular which refers to the net-like pattern. Causes A number of conditions may cause the appearance of livedo reticularis: Cutis marmorata telangiectatica congenita, a rare congenital condition Sneddon syndrome – association of livedoid vasculitis and systemic vascular disorders, such as strokes, due to underlying genetic cause Idiopathic livedo reticularis – the most common form of livedo reticularis, completely benign condition of unknown cause affecting mostly young women during the winter: It is a lacy purple appearance of skin in extremities due to sluggish venous blood flow. It may be mild, but ulceration may occur later in the summer. Secondary livedo reticularis: Vasculitis autoimmune conditions: Livedoid vasculitis – with painful ulceration occurring in the lower legs Polyarteritis nodosa Systemic lupus erythematosus Dermatomyositis Rheumatoid arthritis Lymphoma Pancreatitis Chronic pancreatitis Tuberculosis Drug-related: Adderall (side effect) Amantadine (side effect) Bromocriptine (side effect) Beta interferon treatment, e.g. in multiple sclerosis Livedo reticularis associated with rasagiline Methylphenidate and dextroamphetamine-induced peripheral vasculopathy Gefitinib Obstruction of capillaries: Cryoglobulinaemia – proteins in the blood that clump together in cold conditions Antiphospholipid syndrome due to small blood clots Hypercalcaemia (raised blood calcium levels which may be deposited in the capillaries) Haematological disorders of polycythaemia rubra vera or thrombocytosis (excessive red cells or platelets) Infections (infective endocarditis, syphilis, tuberculosis, Lyme disease) Associated with acute kidney injury due to cholesterol emboli status after cardiac catheterization Arteriosclerosis (cholesterol emboli) and homocystinuria (due to Chromosome 21 autosomal recessive Cystathionine beta synthase deficiency)