Purpura consists of purple-coloured bruises resulting from bleeding under the skin. It occurs when small blood vessels, called capillaries, leak blood into the surrounding tissues. The blood eventually breaks down and changes colour as it is metabolised, leading to a characteristic range of colours over time, from purple to orange, brown, blue, and green. This discolouration can persist for a few weeks as the body gradually reabsorbs the blood.

What are the manifestations of purpura?

Purpura can manifest in various ways, including:

• Petechiae: These are small, pinpoint-sized purple or red lesions with a diameter of up to 2 mm. They typically appear as tiny dots on the skin and are caused by minor bleeding from capillaries
• Ecchymoses: These are larger patches of extravasated blood beneath the skin, commonly known as bruises. Ecchymoses can vary in size and color, ranging from purple to greenish-yellow as they heal
• Vasculitic purpura: This type of purpura involves inflammation of the blood vessels (vasculitis), which can cause purpuric lesions that are palpable, meaning they can be felt when touched. This inflammation may result from various underlying conditions or diseases
• Pigmented purpura: This type of purpura is characterized by petechial haemorrhage associated with capillaritis (leaky capillaries), leading to a distinctive pigmented appearance of the skin

These different manifestations of purpura can provide valuable clues to healthcare providers trying to diagnose and determine the underlying cause of the condition.

Signs and symptoms of purpura 

The signs and symptoms of purpura can vary depending on the underlying cause and type of purpura:

Thrombocytopenic purpura

This condition is characterized by low platelet counts, leading to an increased risk of bleeding. Petechiae, which are small red or purple spots caused by minor bleeding from broken capillaries, is a common feature of thrombocytopenic purpura. Additionally, external haemorrhages and bruising may occur due to impaired blood clotting.

Coagulation disorders

These disorders involve abnormalities in the blood clotting process, leading to difficulties in stopping bleeding. In coagulation disorders, such as haemophilia or disseminated intravascular coagulation (DIC), large ecchymoses (bruises) and external haemorrhages are more common manifestations of purpura. Petechiae, however, are less likely to occur in coagulation disorders when compared to thrombocytopenic purpura.

Vasculitis

Inflammation of the blood vessels, known as vasculitis, can cause localised purpura with an erythematous (red) inflammatory component. Unlike thrombocytopenic purpura and coagulation disorders, petechiae is not a common feature of vasculitis. Instead, the purpura in vasculitis tends to be palpable, meaning it can be felt when touched. Ecchymoses and external haemorrhages are also relatively uncommon in vasculitic purpura.

Recognising these signs and symptoms, along with considering other clinical features and laboratory tests can help healthcare providers diagnose the underlying cause of purpura and determine the appropriate treatment approach.

Purpura (larger red, brown, and purple dots) and petechiae (smaller red and purple dots) in the skin https://www.nhlbi.nih.gov/health/thrombotic-thrombocytopenic-purpura.

Purpura classification

Classification of purpura based on its underlying cause and appearance helps healthcare providers diagnose and manage the condition effectively. Each type may require specific diagnostic tests and treatments tailored to the individual patient's needs.

Vascular disorders

These are characterised by abnormalities in the blood vessels that lead to leakage of blood through the vessel wall. This can result from various factors, including increased intraluminal pressure (pressure inside the blood vessels), damage to small blood vessels, or deficient vascular support.

• Senile Purpura: also known as actinic purpura or solar purpura, this type of purpura occurs predominantly in older individuals with aged or sun-damaged skin. It is characterised by the appearance of purpuric lesions due to the fragility of blood vessels, which can easily rupture from minor trauma or pressure.

Platelet disorders

These disorders involve abnormalities in platelet function or numbers, leading to an increased risk of bleeding and purpura. 

Thrombocytopenic purpura: this type of purpura occurs in approximately 6 to 10 people per million.

It can affect the heart and brain.

Thrombocytopenic purpura can be further classified into:

• Primary (idiopathic) thrombocytopenic purpura: 

This condition occurs due to the autoimmune destruction of platelets or for unknown reasons

• Secondary thrombocytopenic purpura: 

This type of purpura is secondary to external or internal factors such as infections, systemic diseases, or medication use

• How does it happen?

Accumulation of the large Von Willebrand factor (VWF) factor causes the formation of blood clots and leads to a loss of blood platelets

Other coagulation disorders

Disseminated intravascular coagulation (DIC)

DIC is a complex disorder characterised by widespread activation of the clotting cascade (the sequence of steps that lead to the formation of a blood clot), leading to both thrombosis and haemorrhage. It can present with purpura, ranging from severe purpura fulminans to milder forms.

Heparin-induced thrombocytopenia (HIT)

This condition is characterised by purpura and necrosis due to the formation of platelet clots in blood vessels triggered by heparin (blood anticoagulant drug) use.

Warfarin-induced necrosis

Warfarin-induced purpura and necrosis can occur due to blood clots associated with relative protein C deficiency at the start of treatment with warfarin (blood anticoagulant drug).

What is the treatment for purpura?

The cause of purpura should be identified and treated accordingly.

Treatment of Thrombocytopenic purpura 

The treatment of thrombocytopenic purpura primarily focuses on managing platelet levels and preventing further platelet destruction. Treatment includes the use of:

Steroids (such as prednisone)

Steroids are often used as the first-line treatment for thrombocytopenic purpura. They work by suppressing the immune response and reducing the production of antibodies that target platelets, such as ADAMTS13 (a specific enzyme involved in platelet function). By dampening the immune system's activity, steroids help to prevent further destruction of platelets and promote an increase in platelet counts.

Folic acid

Folic acid supplementation is commonly prescribed in conjunction with other treatments for thrombocytopenic purpura. Folic acid is a vitamin that plays a crucial role in the production of new red blood cells. In cases where purpura is associated with anaemia (a decrease in red blood cell count), folic acid supplementation can help support the production of new red blood cells, which may be necessary due to increased turnover or loss of red blood cells.

Rituximab

Rituximab is a monoclonal antibody that targets specific cells of the immune system called B cells. It works by depleting these B cells, which play a role in producing antibodies against platelets (including ADAMTS13 antibodies) in thrombocytopenic purpura. By reducing the population of these B cells, rituximab helps to suppress the immune response and decrease the production of harmful antibodies, thereby preserving platelet levels.

Caplacizumab

Caplacizumab is a new treatment option for thrombotic thrombocytopenic purpura (TTP), a specific subtype of thrombocytopenic purpura characterised by the widespread formation of blood clots in small blood vessels. Caplacizumab works by blocking the interaction between platelets and a protein called Von Willebrand factor, which is involved in blood clot formation. By inhibiting this interaction, caplacizumab helps to prevent the formation of blood clots and reduce the risk of tissue damage associated with TTP.

Low Molecular Weight Heparin (LMWH)

LMWH is a type of anticoagulant medication that is often used to help prevent the formation of blood clots in TTP. While TTP is primarily characterised by the widespread formation of blood clots in small blood vessels, anticoagulants like LMWH can help reduce the risk of further clot formation. LMWH works by inhibiting the activity of certain clotting factors in the blood, thereby preventing the formation of new blood clots and potentially reducing the severity of TTP-related complications.

Plasma exchange (Plasmapheresis)

Plasma exchange, also known as plasmapheresis, is a therapeutic procedure used to remove harmful substances from the blood, including antibodies and other proteins that may contribute to the development of TTP. During plasma exchange, blood is withdrawn from the patient's body, and the plasma (the liquid portion of blood containing antibodies) is separated from the blood cells using a specialised machine called an apheresis machine. The plasma containing harmful antibodies is then discarded, and the remaining blood cells are returned to the patient's body along with replacement plasma from blood donors. This process helps to reduce the levels of harmful antibodies in the blood, thereby decreasing the likelihood of further platelet destruction and blood clot formation in TTP.

These treatments are often used in combination or sequentially, depending on the severity of the condition and individual patient factors. As always, the specific treatment approach should be tailored to the individual patient's needs and guided by a healthcare provider experienced in managing thrombocytopenic purpura. Regular monitoring and follow-up are essential to assess treatment response and adjust therapy as needed.

Risks associated with the treatment

• Thrombosis: One of the main concerns with treatments for TTP, particularly plasma exchange, is the risk of thrombosis or blood clot formation. While plasma exchange helps remove harmful antibodies and proteins from the blood, it can also disrupt the balance of clotting factors, potentially increasing the risk of thrombosis. This risk is particularly heightened in patients with central venous catheters or other forms of central access used for plasma exchange. Close monitoring and appropriate anticoagulant therapy are often necessary to mitigate this risk
• Infection: Central venous catheters used for plasma exchange or other treatments can increase the risk of infection, including bloodstream infections (septicemia) and local infections at the catheter insertion site. Strict adherence to sterile techniques during catheter placement and maintenance, as well as regular monitoring for signs of infection, are essential to minimise this risk
• Bleeding: While anticoagulant therapy like low molecular weight heparin is used to prevent blood clot formation in TTP, it can also increase the risk of bleeding, particularly in patients with pre-existing bleeding disorders or other risk factors for haemorrhage. Careful monitoring of coagulation parameters and adjustment of anticoagulant dosages are necessary to balance the risk of bleeding with the need for thromboprophylaxis (preventative measures to reduce the risk of thrombosis)
• Allergic reactions: Some patients may experience allergic reactions or hypersensitivity to certain medications used in the treatment of TTP, such as rituximab or caplacizumab. These reactions can range from a mild rash or itching to severe anaphylaxis and require prompt recognition and management

Overall, while the aforementioned treatments are crucial for managing TTP and preventing potentially life-threatening complications, healthcare providers must carefully weigh their benefits and risks for each patient and take appropriate measures to minimise adverse outcomes. Close monitoring, patient education, and multidisciplinary care are essential components of the management of TTP.

Summary 

Purpura manifests as a change in the colour of the skin or mucous membranes due to bleeding from small blood vessels. It is crucial to diagnose and treat purpura according to its underlying cause, which can vary widely. Identifying the cause of purpura is essential to determine the most effective treatment approach and minimise potential complications associated with the condition.