Purpura

What is purpura?

Purpura is a sign, not a disease. It means blood has escaped from capillaries or small vessels into the skin or mucous membranes. Because the blood is outside the vessels, pressing on the spot does not push it away. That is why purpura does not blanch, while most rashes, which are caused by widened vessels, fade under pressure.

Petechiae vs purpura vs ecchymosis

The glass test

Press the side of a clear drinking glass firmly against the spots. If they stay visible through the glass, they are non-blanching. In someone who is unwell or has a fever, this needs emergency care. On darker skin, purpura can be harder to see, so check paler areas such as the palms, soles, inside the eyelids and the roof of the mouth.

Causes of purpura

Problems with platelets

Platelets plug small leaks in blood vessels. When they are low (thrombocytopenia) or do not work properly, petechiae and purpura appear.

• Immune thrombocytopenia (ITP): the immune system destroys platelets. Common in children after a viral illness, usually self-limiting. In adults it is more often long-term.
• Thrombotic thrombocytopenic purpura (TTP): small clots use up platelets, with fever, confusion and kidney injury. A medical emergency.
• Leukemia and other marrow diseases: abnormal cells crowd out platelet production. See leukemia.
• Medicines: heparin, some antibiotics, quinine, anti-seizure drugs, and drugs that impair platelet function such as aspirin, clopidogrel and NSAIDs.
• Liver disease, enlarged spleen, viral infections and pregnancy-related conditions.

Problems with clotting factors

• hemophilia and von Willebrand disease
• vitamin K deficiency and blood thinners such as warfarin
• disseminated intravascular coagulation (DIC), in which severe illness uses up clotting factors and platelets

These more often cause larger bruises and joint or muscle bleeding than pinpoint petechiae.

Problems with blood vessels or skin

• Senile (actinic) purpura: dark purple patches on the forearms and backs of the hands in older adults with sun-damaged, thin skin. Minor bumps cause them. They fade over 1 to 3 weeks and often leave brown staining. Harmless.
• Steroid purpura: long-term steroid tablets or creams thin the skin. A similar effect occurs in Cushing syndrome.
• Vasculitis: inflammation of small blood vessels causes palpable purpura, mostly on the legs. IgA vasculitis (Henoch-Schonlein purpura) in children also causes joint pain, belly pain and blood in the urine. See vasculitis.
• Pressure and straining: petechiae on the face, neck and around the eyes after vomiting, coughing fits, childbirth or heavy lifting. They fade within a few days.
• Scurvy (vitamin C deficiency): spots around hair follicles, corkscrew hairs and bleeding gums.
• Amyloidosis: bruising around the eyes ("raccoon eyes") after minor strain.

Infections

• Meningococcal disease: a rapidly spreading non-blanching rash with fever. It can be fatal within hours and needs immediate antibiotics.
• Sepsis from other bacteria, Rocky Mountain spotted fever, dengue and other viral hemorrhagic fevers.

How doctors find the cause

A doctor will ask about medicines, recent infections, bleeding elsewhere, and family history, and look at the pattern of spots and whether they are raised. Tests usually include:

• complete blood count and blood smear: platelet count, signs of leukemia, fragmented red cells in TTP
• clotting tests: PT/INR, aPTT and fibrinogen
• kidney and liver function and urinalysis, especially when vasculitis or TTP is possible
• blood cultures when infection is suspected
• skin biopsy for palpable purpura to confirm vasculitis
• bone marrow biopsy if blood counts suggest a marrow problem

Treatment

Treatment targets the cause:

• Infection-related purpura: emergency antibiotics and intensive care.
• ITP: observation in many children, steroids or immune globulin when platelets are very low or bleeding occurs, and other medicines for persistent cases.
• TTP: emergency plasma exchange and immune treatment.
• Medicine-related: stopping the drug under medical advice.
• Vasculitis: treating the trigger, pain relief, and steroids or immune-suppressing drugs for organ involvement.
• Senile purpura: no treatment needed. Protect the skin from bumps, use moisturizer and sunscreen, and consider long sleeves.

Frequently asked questions

What is purpura?

Purpura is bleeding under the skin that shows as red, purple or brown spots or patches that do not fade when pressed. It can be caused by low or poorly working platelets, clotting problems, fragile or inflamed blood vessels, or infections. The cause decides how serious it is.

What is the difference between petechiae and purpura?

They are the same process at different sizes. Petechiae are pinpoint spots under 3 mm. Purpura are larger spots from about 3 mm to 1 cm. Patches over 1 cm are called ecchymoses, or bruises.

When should I worry about purpura?

Seek emergency care for purpura with fever, a stiff neck, drowsiness or if the person seems very unwell, and for spots that spread quickly. See a doctor soon for unexplained purpura with bleeding gums, nosebleeds, tiredness or bone pain, which can signal low platelets or leukemia.

What causes purple patches on the arms of older adults?

These are usually senile, or actinic, purpura. Years of sun damage and aging make the skin and small vessels fragile, so minor knocks cause flat purple patches on the forearms and hands. They are harmless and fade over a few weeks. Blood thinners make them more common.

Is purpura a sign of leukemia?

It can be. Leukemia crowds out platelet production, causing petechiae and easy bruising, often with tiredness, pale skin, infections or bone pain. Most purpura has other causes, but a simple blood count can check for leukemia.