Petechiae and purpura
Purpura are larger areas of bleeding into the skin that begin as red areas that become purple and later brownish-yellow. Purpura usually appears in crops and may disappear over three to five days. It can occur on any part of body but is more common on specific areas, such as the front of the shins.
Petechiae are pinpoint-sized hemorrhages of small capillaries in the skin or mucous membranes. Petechiae is the term given to the individual small red or red-blue spots about 1-5mm in diameter which make up the rash.
They are caused by a small local amount of bleeding within the skin. Deeper bleeding beneath the skin may be seen as bruises (ecchymoses). The difference between petechiae and abnormally prominent blood vessels can be shown by applying pressure to a red spot. If it is caused by an abnormal blood vessel the redness disappears temporarily. By contrast when pressure is applied to purpura the spots do not pale.
Petechiae result from tiny areas of superficial bleeding into the skin. They appear as round, pinpoint-sized dots that are not raised. The color varies from red to blue or purple as they age and gradually disappear. Petechiae commonly appear on the lower legs, but may be distributed all over the body. Petechiae that appear during illness, especially illness with fever, can be a different story. Because the presence of bacteria in the bloodstream (classically Meningococcus, the causative agent of "spinal meningitis") can be heralded by the appearance of petechiae, these little marks are searched for during the skin examination of a sick child. If present, they could be be the heralds of very dangerous sepsis, even in a child who does not look all that ill.
Petechiae are red because they contain red blood that has leaked from the capillaries into the skin. Petechiae are quite tiny (less than 3 millimeters in diameter) and do not blanch when pressed upon. There are many conditions in which petechiae may be seen. These conditions range from very minor to very major. The common causes of petechiae include local injury and trauma, allergic reactions, autoimmune diseases, viral infections that impair blood coagulation (clotting), thrombocythemia (an abnormally high platelet level), certain medical treatments such as radiation and chemotherapy, idiopathic thrombocytopenic purpura (ITP), leukemia and other bone marrow malignancies that may lower the number of platelets, and sepsis (bloodstream infection). Petechiae are normally seen right after birth in the newborn and after violent vomiting or coughing. Drugs such as the anticoagulants warfarin (Coumadin) or heparin, aspirin, and cortisone can also cause petechiae.
Purpura may occur when the platelet count of the blood is low (thrombocytopenia) but there are other causes too. It can occur when the blood vessel wall is particularly fragile, has been damaged, or if the skin is thin. In elderly people so-called 'senile purpura' is often seen on the outer surface of the arm and back of the hand. Similar features are seen in some patients treated with long-term steroid therapy because steroids weaken the connective tissues of the skin. In some inflammatory conditions damage to the vessel wall, or 'vasculitis', may occur and can cause purpura. An example is the inflammatory disorder in children known as Henoch Schönlein purpura. In this there is abdominal pain, joint pain, kidney inflammation and raised purpura typically over the buttocks and limbs. Purpura with painful bruising of the legs and around hair roots may also be seen in vitamin C deficiency or scurvy. Purpura should be reported to a doctor for further investigation. In a person who is otherwise well this investigation can be done routinely. However, if the person with purpura is unwell, urgent investigation and treatment is required.
Treatment is directed at the underlying cause of the petechiae. For example, someone with petechiae caused by an infection is given antibiotics. If petechiae are caused by allergy to a medication, the medication may need to be stopped. A person with petechiae due to a low platelet count may need a transfusion of platelets or other blood factors. A person with leukemia or cancer may need surgery, chemotherapy, or radiation therapy. Petechiae caused by injury need no treatment. Applying an ice pack off and on for 24 hours after the injury may reduce further petechiae. The petechiae will fade in time.
It is not always possible to avoid petechiae. Avoiding trauma will help prevent petechiae caused by injury. If allergy to a medication is the cause, avoiding the medication will help prevent the condition. Prompt treatment of infections will help prevent sepsis.