Causes of Purpura: Purple Spots on Skin

Purpura, known as purple spots or patches on the skin, is caused by small blood vessels leaking under the skin. It can occur on the skin and mucous membranes, including the lining of the mouth. Purpura has a wide array of possible causes that range from a temporary drug side effect to a sign of a serious underlying medical condition. 

Close up of bruised skin on human leg

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What Is Purpura?

When small blood vessels beneath the skin start to leak blood, they cause tiny purple dots or larger purple patches to appear on the skin. Purpura may be temporary or a sign of an underlying medical condition.

There are two main types of purpura: nonthrombocytopenic and thrombocytopenic. They are classified by whether platelets are involved. Platelets are cells in the bloodstream that work to clot blood and prevent bleeding. Thrombocytopenic purpura is caused by low platelet counts, while nonthrombocytopenic purpura is not related to the number of platelets in your blood.

The size and distribution of purpura are usually determined by what is causing them in the first place. When purpura spots are less than 4 millimeters in diameter, they are called petechiae. Purpura spots larger than 1 centimeter are called ecchymoses.

Nonthrombocytopenic

Individuals who experience nonthrombocytopenic purpura have normal platelet levels. They may be experiencing bleeding due to altered platelet function or inflammation. If blood vessels are damaged, they can begin to leak blood even if platelet counts are sufficient. 

Conditions that can lead to nonthrombocytopenic purpura include:

  • Senile purpura, also known as solar purpura, affects older individuals who have thinner skin and more fragile blood vessels. While it looks concerning, this type of purpura is usually mild and resolves on its own. 
  • Vasculitis is a condition characterized by inflammation of the blood vessels in the skin, gastrointestinal tract, and kidneys. IgA vasculitis, previously known as Henoch-Schönlein purpura, and leukocytoclastic vasculitis are among the subsets of this condition that can cause purpura.

Signs

Signs of nonthrombocytopenic purpura vary based on the cause. Senile purpura is characterized by ecchymoses on the hands and forearms, while symptoms of IgA vasculitis include a skin rash and joint pain. 

Causes

Causes of nonthrombocytopenic purpura can include blood vessel changes, inflammation, viruses, and medications. Senile purpura is caused by a thinning and weakening of the skin and blood vessels. These changes are usually related to damage from the sun’s UV rays, as well as aging and drugs like warfarin or aspirin. 

IgA vasculitis leads to purpura because of inflammation. When blood vessels experience inflammation, they become damaged and red blood cells leak out, causing the fine rash. IgA vasculitis usually occurs after a respiratory illness, such as strep throat, but the exact cause is still unknown. 

Other possible causes of nonthrombocytopenic purpura include:

  • Amyloidosis is a rare medical condition that causes abnormal proteins to build up in the body’s organs and tissues. This buildup of proteins leads to inflammation, which can cause purpura. 
  • Congenital cytomegalovirus occurs when an infant is born with cytomegalovirus and became infected while in utero. Most babies do not have symptoms, but some are born with a fine purpura rash.
  • Congenital rubella is a syndrome in which a baby is infected with rubella (German measles) before they are born. This causes a host of serious health problems, including purpura.
  • Scurvy is a disease caused by vitamin C deficiency. It is rare in the United States and is characterized by fine red and purple dots over the skin.

Steroid use and injury can also lead to purpura.

Treatment

Not all types of nonthrombocytopenic purpura require treatment. As long as senile purpura does not lead to serious bleeding, the purple spots and patches will resolve on their own. 

Mild cases of IgA vasculitis should also resolve on their own without medical treatment. Because this condition also causes joint pain, it is usually treated with over-the-counter pain medications like acetaminophen and ibuprofen. If the condition seems more severe or if there is noted kidney damage, your doctor may recommend immunosuppressive medications. This is because IgA vasculitis is believed to be caused by an overreaction of the immune system. 

IgA vasculitis causes the small blood vessels in your skin, joints, intestines and kidneys to become inflamed and bleed. While this condition can happen to individuals of any age, it is most common in children between the ages of 2 and 6. It is also more common in boys than girls. Each year, about 10 out of 100,000 children are diagnosed with IgA vasculitis. 

Thrombocytopenic Purpura

Thrombocytopenia is a condition in which your blood platelet count is low. Platelets, also known as thrombocytes, work to clot the blood by clumping together to stop bleeding. People who have thrombocytopenia don’t have enough platelets to form a blood clot. If they get a cut or other injuries, they may bleed too much and the bleeding can be hard to stop. Thrombocytopenia occurs when platelets are damaged, sequestered, or decreased.

Signs

Signs of thrombocytopenic purpura include both tiny purple dots and larger purple patches of skin. Other symptoms of thrombocytopenia include:

  • Bleeding gums
  • Blood in stool, urine, or vomit
  • Rectal bleeding
  • Heavy menstrual bleeding

Causes

Thrombocytopenia can be caused by conditions that damage the platelets, decrease platelet production, or cause platelet sequestration. These conditions include:

  • Idiopathic thrombocytopenic purpura (ITP): Also called immune thrombocytopenic purpura, this bleeding disorder occurs when the immune system destroys platelets. The immune system produces antibodies that attach to platelets, and the body destroys the platelets that carry the antibodies.
  • Neonatal alloimmune thrombocytopeniaThis condition occurs in infants whose mothers have ITP. The antibodies can cross the placenta and attach to the baby's platelets.
  • Meningococcemia: This is a bloodstream infection caused by bacteria called Neisseria meningitidis. The bacteria often live in a person's upper respiratory tract without causing signs of illness. They can be spread from person to person through respiratory droplets. 

Certain drugs like chemotherapy medications damage platelets, resulting in a low level of these cells. Bone marrow diseases can also cause a decrease in the production of platelets because these tissues are responsible for producing blood cells in the body, including platelets. 

Splenic sequestration occurs when blood is trapped and starts to pool in the spleen. When this happens, platelets do not travel throughout the body via the bloodstream as they are supposed to.

Treatment

Treatment for thrombocytopenic purpura depends on the cause. Usually, once the underlying cause is treated, purpura will resolve. In children with ITP, the disease usually goes away on its own without treatment, but some may require medical interventions. Adults are usually started on a steroid medicine, prednisone or dexamethasone, and may need to have their spleens removed through a splenectomy to increase platelet levels. If your platelet count is dangerously low, your doctor may recommend a platelet or blood transfusion as well. 

A splenectomy may also be indicated if the thrombocytopenia is caused by an enlarged spleen. Because your spleen is part of your immune system, a splenectomy can put you at higher risk of infection. Medications like steroids and immunoglobulins can help to stimulate new platelet production and stop any destruction of platelets.

Other Types of Purpura

There are other types of purpura that do not fit into the thrombocytopenic or nonthrombocytopenic categories. These types are usually quite serious and require immediate intervention:

  • Disseminated intravascular coagulation (DIC) leads to purpura not because of a lack of blood clotting, but because of too much of it. This serious condition causes proteins that control blood clotting to become overactive.
  • A severe reaction to heparin, an anticoagulant used to prevent blood clots, called heparin-induced thrombocytopenia causes widespread blood clotting throughout the body. This occurs when the body recognizes heparin as a foreign invader and creates antibodies against it. When these antibodies bind to heparin in the bloodstream, the platelets are activated and too much clotting occurs. One of the first signs of heparin-induced thrombocytopenia is purpura. 
  • In rare cases, warfarin, another anticoagulant medication, can lead to warfarin-induced skin necrosis. Skin necrosis refers to the premature death of skin cells. Purpura is usually one of the first signs. 

Signs

DIC is characterized by both bleeding and blot clots, and purpura can appear over the body. Other signs of DIC include fever, hypotension, shortness of breath, and confusion.

Heparin-induced thrombocytopenia causes purpura, pain, and redness. You may also see redness or a rash at the site where the heparin was administered. Later signs include numbness and weakness.

Warfarin-induced skin necrosis starts with purpura, followed by skin lesions and hemorrhagic blisters. 

Causes

DIC is most often caused by infection, inflammation, or cancer. It is possible to experience DIC because of a reaction to a blood transfusion, certain cancers, pancreatitis, liver disease, pregnancy complications, tissue injury, infection, or hemangioma. 

Heparin-induced thrombocytopenia is caused by an immune response to heparin, while warfarin-induced skin necrosis is related to taking the drug warfarin. This complication of warfarin is rare, and an underlying protein C deficiency may put patients more at risk. 

Treatment

In the case of DIC, plasma transfusions and blood-thinning medication can help to treat the symptoms while the initial cause is being treated. 

Heparin-induced thrombocytopenia requires immediate treatment. First, heparin therapy has to be stopped; warfarin may be administered to address the blood clots. Other anticoagulants like aspirin may be needed as well.

Warfarin-induced skin necrosis treatment starts with stopping warfarin therapy and administering IV vitamin K to assist in blood clotting. Treatment with prostaglandins and monoclonal antibodies may be given as well. 

A Word From Verywell

Purpura may look concerning, but some types of purpura are actually harmless and go away on their own without treatment. Knowing the cause of purpura will determine whether you need treatment for your purpura spots. Thrombocytopenic purpura is caused by a low platelet level, while nonthrombocytopenic purpura has other causes unrelated to the platelet level in the blood. If you have recently noticed new purple spots or patches over your skin, see your doctor to determine the cause and start the appropriate treatment. 

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Article Sources
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