Causes of Purpura: Purple Spots on Skin

Purpura means you have dark spots or patches on the skin. They're purple on light skin and dark brown or black on darker skin.

Spots are caused by leaks in small blood vessels. They can show up on the skin and mucous membranes. That includes the lining of your mouth.

Purpura has a wide array of possible causes. They range from a temporary drug side effect to a sign of a serious medical condition. 

This article looks at the types, symptoms, and causes of purpura and how they're treated.

Types of Purpura

The main types of purpura are defined by whether platelets are involved. Platelets (thrombocytes) are cells in your blood that cause clots and prevent excessive bleeding.

A condition called thrombocytopenia involves low platelets. It causes bruising, bleeding into tissues, and slow blood clotting.

• Thrombocytopenic purpura is caused by low platelet counts.
• Nonthrombocytopenic purpura isn't related to platelets.

Other types of purpura don't fit into these categories. Instead, they're tied to more serious conditions.

The size and distribution of purpura are usually determined by what's causing them. Spots less than 4 millimeters (mm) in diameter are called petechiae. Spots larger than 1 centimeter (cm) are called ecchymoses.

Thrombocytopenic Purpura

Thrombocytopenic purpura (TP) is a consequence of thrombocytopenia. When platelets are low, blood doesn't clot properly. It can be hard to stop bleeding from cuts and scrapes.

TP has other bleeding-related symptoms, several causes, and a variety of treatments.

Signs

Thrombocytopenic purpura causes tiny purple or dark dots and larger patches. It's one symptom of thrombocytopenia. Other symptoms include:

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

Causes

TP is caused by thrombocytopenia. Thrombocytopenia can be caused by conditions that affect the platelets. These include:

• Immune (or idiopathic) thrombocytopenia: An autoimmune disease in which your immune system destroys platelets. It does this with antibodies.
• Neonatal alloimmune thrombocytopenia: Immune thrombocytopenia during pregnancy can allow antibodies to cross the placenta and attack the baby's platelets.
• Meningococcemia: A bloodstream infection caused by Neisseria meningitidis bacteria. It spreads from person to person through respiratory droplets. 
• Splenomegaly: The spleen becomes enlarged and function is impaired. This makes it hold on to platelets, so they can circulate in your bloodstream.

Chemotherapy drugs can damage platelets, as well. That leads to low levels.

Treatment

Treatment for TP depends on the cause. It usually resolves once the cause is treated.

Typical first-line treatments include:

• Corticosteroid medication: Stops the destruction of platelets, which quickly raises counts.
• Intravenous immunoglobulin (IVIg): Raises platelets quickly.

In persistent or chronic cases, treatments may be:

• Monoclonal antibodies: Suppress part of the immune system to slow or stop platelet destruction.
• TPO-RAs (thrombopoietin receptor agonists): Increase platelet production.
• Platelet or blood transfusion: Adds platelets or blood directly into your system. Typically just used when the platelet count is dangerously low.
• Splenectomy: Surgical removal of the spleen.

In children, ITP usually goes away without treatment. If it doesn't, the above treatments may be used.

Nonthrombocytopenic

Nonthrombocytopenic purpura (NTP) involves bleeding due to altered—not low—platelet function or inflammation. Damaged blood vessels leak even though platelet counts are in the normal range. 

Conditions that can lead to NTP include:

• Senile (or solar) purpura: Affects older people with thinner skin and more fragile blood vessels. It looks concerning but is usually mild and resolves on its own. 
• Some types of vasculitis: Cause purpura through inflammation of the blood vessels in the skin, gastrointestinal tract, and kidneys.

Leukocytoclastic or IgA vasculitis (formerly Henoch-Schönlein purpura) are among the types of vasculitis that can cause purpura.

Signs

Signs of nonthrombocytopenic purpura vary based on the cause.

Senile purpura causes ecchymoses on the hands and forearms. IgA vasculitis symptoms include a skin rash and joint pain.

Causes

Causes of nonthrombocytopenic purpura can include:

• Blood vessel changes
• Inflammation
• Viruses
• Medications

Senile purpura is caused by thinning and weakening skin and blood vessels. These changes are usually related to sun damage, aging, or blood-thinning drugs like Coumadin (warfarin) or aspirin. 

IgA vasculitis-related purpura is due to inflammation. Inflammation damages blood vessels and allows red blood cells to leak and cause a fine rash. It usually follows a respiratory illness, such as strep throat, but the exact cause is unknown. 

IgA vasculitis can happen at any age but is most common between the ages of 2 and 6. It's also more common in boys than girls. 

Other possible causes of NTP include:

• Amyloidosis: A rare medical condition in which abnormal proteins build up in your organs and tissues. That causes inflammation, which can lead to purpura. 
• Congenital cytomegalovirus: An infant is infected with cytomegalovirus in the womb and is then born with it. If it's symptomatic, it can cause a fine purpura rash.
• Congenital rubella: An infant is infected with rubella (German measles) before birth. This causes purpura plus a host of serious health problems.
• Scurvy: A disease caused by vitamin C deficiency that's characterized by fine red and purple dots over the skin. It's rare in the United States.

Long-term steroid use can cause purpura by destroying collagen, which is a component of small blood vessels.

Treatment

Nonthrombocytopenic purpura doesn't have specific treatments. If it's caused by an underlying condition, treating that condition may help.

Otherwise, senile and IgA vasculitis-related cases usually go away on their own. Some people use alpha-hydroxy acid cream or tretinoin cream to make skin thicker.

Wear protective sleeves can help prevent bumps and bruises that lead to purpura. Some people prefer to cover the spots with makeup.

The mild joint pain of IgA vasculitis is usually treated with over-the-counter (OTC) pain medications. These include Tylenol (acetaminophen) and Advil/Motrin (ibuprofen).

Some cases of IgA vasculitis are severe or include kidney damage. It's thought to be caused by an overactive immune system. So immunosuppressants are used to treat them.  

Other Types of Purpura

Other types of purpura don't fit into the thrombocytopenic or nonthrombocytopenic categories. They're usually quite serious and require immediate treatment.

• Disseminated intravascular coagulation (DIC): The purpura of DIC isn't from poor clotting but from too much of it. It makes proteins that control blood clotting overactive.
• Heparin-induced thrombocytopenia: Heparin is a drug used to prevent blood clots (anticoagulant). A severe reaction to it causes widespread blood clotting throughout the body. 
• Warfarin-induced skin necrosis: In rare cases, the anticoagulant drug warfarin can lead to the premature death of skin cells. Purpura is usually one of the first signs. 

Signs

Signs of DIC include:

• Bleeding and blot clots
• Purpura all over the body
• Fever
• Hypotension
• Shortness of breath
• Confusion

Heparin-induced thrombocytopenia causes:

• Purpura
• Pain
• Redness

You may also have redness or a rash where the heparin was administered. Later signs include numbness and weakness.

Warfarin-induced skin necrosis starts with purpura, then progresses to:

• Bluish-black skin lesions with a red rim
• Blood-filled blisters
• Skin death

This condition most often affects:

• Breasts
• Thighs
• Buttocks
• Hips
• Abdomen
• Toes (called blue toe syndrome)

Causes

DIC is most often caused by:

• Infection
• Inflammation
• Cancer.

Less often, it can be due to:

• A reaction to a blood transfusion
• Certain cancers
• Pancreatitis
• Liver disease
• Pregnancy complications
• Tissue injury
• Infection
• Hemangioma

Heparin-induced thrombocytopenia is caused by an immune response to heparin. Your body recognizes heparin as a foreign invader and creates antibodies against it.

Then antibodies bind to heparin in the bloodstream That activates platelets, which causes too much clotting. Purpura is one of the first signs of heparin-induced purpura.

Warfarin-induced skin necrosis is a rare complication of taking the drug warfarin. You may be more at risk if you have a C deficiency. 

Treatment

For DIC, the cause of purpura needs to be treated. Meanwhile, plasma transfusions and blood-thinning medication can help treat the symptoms. 

Heparin-induced thrombocytopenia requires immediate treatment.

• First, heparin therapy has to be stopped.
• Warfarin may be used to clear up blood clots.
• Other anticoagulants like aspirin may be used as well.

Warfarin-induced skin necrosis treatment consists of:

• Stopping warfarin therapy.
• Using IV vitamin K to help with blood clotting.
• Possible treatment with prostaglandins and immunosuppressants. 

Summary

Purpura causes dark or purples spots or patches on your skin. Thrombocytopenic purpura is caused by low platelets in the blood. Nonthrombycytopenic purpura and other types are not.

Nonthrombocytopenic purpura often doesn't need to be treated. The others do. The treatment depends on the cause. Heparin-induced thrombocytopenia needs immediate treatment.

Usually, the focus of treatment isn't the purpura itself, but the underlying condition that triggered it.

A Word From Verywell

The spots of purpura can be a sign of a serious illness. But more often, they're not serious. Still, the way they look might be a problem for you.

If you develop purpura, see your healthcare provider so you know what's causing it. They can guide you to the right treatment. They also may be able to suggest ways to get rid of or conceal the spots until they clear up.