Petechiae appear due to minor bleeding from tiny blood vessels, known as capillaries, that lie under the skin and mucous membranes. Although there are many causes that can lead to petechiae, the underlying mechanisms typically involve damage to the blood vessel walls that makes the capillaries leak or a low blood platelet count (i.e., thrombocytopenia), which can lead to spontaneous bleeding in the absence of trauma.
Tiny petechiae that appear on the face, neck, and upper chest are often caused by capillaries that rupture due to prolonged straining during a bowel movement or severe bouts of coughing or vomiting. Petechiae may also occur as a result of traumatic injuries, sunburns, or as a side effect of certain medications, such as antibiotics and anticonvulsants.
In children, infections are a common cause of
petechiae. Viruses, like
cytomegalovirus (CMV),
Epstein-Barr virus (EBV), or
influenza; bacteria, including
Neisseria meningitidis and group A
Streptococcus species; and fungi, such as
Candida and
Aspergillus species, can all be sources of
petechiae-inducing infections. Other, less common infections that can lead to
petechiae include
Rocky Mountain spotted fever, which is transmitted by a tick bite, and viral hemorrhagic fevers, such as
dengue,
ebola, and
yellow fever. Overall, infections can lead to
petechiae through several different mechanisms, including damage to the blood vessel walls, toxin release, or uncontrolled activation of
coagulation, which in turn can lead to a low blood platelet count.
Other than certain infections, pathological causes of
petechiae include bone marrow failure, which refers to a decreased production of
platelets and red and white blood cells;
leukemia, which is a type of blood cancer; and other disorders leading to thrombocytopenia, such as
immune thrombocytopenic purpura (ITP),
hemolytic uremic syndrome (HUS), and
disseminated intravascular coagulopathy (DIC). Finally,
petechiae may be a sign of systemic conditions, including blood vessel wall inflammation (i.e.,
vasculitis); connective tissue disorders with increased blood vessel fragility; chronic liver disease; and
vitamin C or
vitamin K deficiency.