Livedo reticularis

What is your differential diagnosis?

Idiopathic livedo reticularis – the most common form of livedo reticularis and is a 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. 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
Rheumatoid arthritis
Amantadine (drug)

Obstruction of capillaries:

Cryoglobulinaemia – proteins in the blood that clump together in cold conditions.[9]
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 (syphilis,tuberculosis, lyme disease)
Assc with Acute Renal Failure due to cholesterol emboli status post cardiac cath.
Arteriosclerosis (cholesterol emboli)[10][11] and homocystinuria (due to Chromosome 21 autosomal recessive Cystathionine beta synthase deficiency)
Intra-arterial injection (especially in drug addicts)

Ehlers-Danlos Syndrome — connective tissue disorder, often with many secondary conditions. Livedo Reticularis may be present in all types.

Courtesy of Wikipedia!