Purpura is purple-colored spots and patches that occur on the skin, and in mucus membranes, including the lining of the mouth.

Considerations
Purpura occurs when small blood vessels leak blood under the skin. Purpura measure between 4 and 10 mm (millimeters) in diameter. When purpura spots are less than 4 mm in diameter, they are called petechiae. Purpura spots larger than 1 cm (centimeter) are called ecchymoses. Platelets help the blood clot. A person with purpura may have normal platelet counts (non-thrombocytopenic purpuras) or low platelet counts (thrombocytopenic purpuras).

Causes of Purpura
Non-thrombocytopenic purpuras may be due to:
-- Thrombocytopenia
-- Amyloidosis
-- Blood clotting disorders
-- Congenital cytomegalovirus
-- Congenital rubella syndrome
-- Drugs that affect platelet function
-- Fragile blood vessels seen in older people (senile purpura)
-- Hemangioma
-- Inflammation of the blood vessels (vasculitis)
-- Pressure changes that occur during vaginal childbirth
-- Scurvy (vitamin C deficiency)

Thrombocytopenic purpura may be due to:
-- Drugs that reduce the platelet count
-- Idiopathic thrombocytopenic purpura (ITP)
-- Immune neonatal thrombocytopenia (can occur in infants whose mothers have ITP)
-- Meningococcemia, a raised type of purpura