Bleeding into the skin may occur for local reasons or as part of a systemic disorder. The distribution of lesions is important: widespread lesions suggest a systemic problem, whereas regional lesions suggest that local factors predominate. Widespread flat purpura without erythema should prompt a search for underlying haematological abnormalities such as platelet disorders. In patients with acute peripheral ischaemia, it is important to exclude embolism. A pressure ulcer (decubitus ulcer, bedsore, pressure sore) is due to localized injury to the skin and/or underlying tissue as a result of pressure alone, or in combination with shear and/or friction. Meanwhile, acute deep venous thrombosis may be silent but usually results in skin erythema and limb oedema. Consequences of post-thrombotic vein damage include further deep venous thrombosis, superficial thrombophlebitis, oedema, skin changes, and eventually ulceration.