There are capillaries under the skin which connect the small veins with the small arteries. When blood leaks, or bleeds in these capillaries, it manifests as petechiae on the skin. This may occur in disease conditions where blood clotting mechanisms inside the body are defective, or in cases where the number of platelets in the circulation are lower than normal.
Petechiae are seen as clusters of tiny red dots, about one to three millimeters each, that appear anywhere in the body, commonly in the ankle, feet and legs. They are often not raised or elevated from the skin. Their presence is frequently an indication of an underlying medical condition. Here are the common causes of petechiae:
Direct injury or trauma to the skin can cause the formation of petechiae. The number of petechiae is usually dependent on the severity of the trauma, with the most severe skin trauma showing as bruises that are often wider and may vary in color as they heal.
Intake of Medications
Intake of drugs, like those prescribed for diabetes and chemotherapy, may also lead to petechiae in susceptible individuals. Corticosteroids and warfarin are other drugs that can also present with petechiae formation.
As a Symptom of Disease
Petechiae formation is usually a symptom that may be seen in several diseases that affect the human body. Examples of these diseases are infections, autoimmune diseases, cancer and nutrient deficiency.
Infections, especially viral infections often present with petechiae in the skin of affected individuals. Examples of these common viral infections, seen especially in children, are measles, dengue hemorrhagic fever, infectious mononucleosis, and idiopathic thrombocytopenic purpura (ITP), a blood clotting defect that usually occur after a viral infection. Most children recover from ITP without much treatment, but adults may have it longer. Hemolytic uremic syndrome, which occurs after several days of bloody diarrhea due to Escherichia coli infection, also presents with petechiae.
Autoimmune diseases are conditions where the body attacks its own cells. Examples of these autoimmune conditions which may present with petechiae are lupus erythematosus and rheumatoid arthritis.
Leukemia, or cancer of the blood, is characterized by the proliferation of young or immature white blood cells (WBC) in the circulation. There are several types of leukemia, some more common in children and other in adults. In most of these cases, petechiae and bruises may form due to the effect of cancer on the ability of the bone marrow to produce platelets.
Lack of certain nutrients in the diet may also present with petechiae formation. One example is scurvy which results from lack of Vitamin C. Vitamin K is an important factor in blood clotting mechanism and its deficiency frequently leads to easy bruising and petechiae development.
One of the common causes of petechiae in the elderly is senile purpura. Senile purpura is a condition brought about by the aging process on the skin. As people age, their skin becomes thin and are more fragile, which makes formation of petechiae and bruises easy. There usually is no underlying medical condition or nutrient deficiency associated with this.
Mayo Clinic: Petechiae