Introduction

Purpura is a clinical manifestation characterised by a red-brown lesion that is caused by localised haemorrhage (leakage of blood from blood vessels) under the skin.¹ They are either acular (flat) or palpable (raised or indurated). Haemorrhage occurs beneath the skin and is due to changes and damage to the internal environment of the body, which leads to inflammation around the lesion. 

Typically, they are divided into either petechiae (non-inflammatory macular purpura ≤4 mm) or ecchymoses (non-inflammatory macular purpura ≥1 cm) depending on the size of the lesion.² These can be found on organs or mucosal membranes, for instance, inside the mouth.³ 

Purpura can be caused by a number of conditions. These can either be benign or life-threatening disorders. For example, benign conditions may include: trauma or injuries, platelet dysfunction or low platelet count, and medications or vitamin deficiencies. Whereas, life-threatening conditions may include vasculitis (an inflammation of blood vessels), sepsis, leukaemia, coagulation disorders, and more.⁴ 

Therefore, purpura must be differentiated from other skin conditions, which present with similar symptoms to prevent misdiagnosis. This way, treatment can be provided appropriately for beneficial outcomes.⁵ 

Dermatologists are required to carry out certain procedures to help prevent diagnostic errors. These include understanding the condition and its differentials, clinical features, interpreting laboratory findings, and using the appropriate diagnostic techniques to help distinguish this condition from other dermatological disorders.  

Overview of purpura 

Purpura refers to a purple or red skin discolouration caused by haemorrhage in the skin or mucosal membrane. The blood leakage is due to a rupture of small blood vessels, which can be terminal arterioles, capillaries, or postcapillary venules.⁶ 

The severity of the condition is determined by the amount of blood that leaks from the blood vessel. They can range in sizes; therefore, it is important to be able to identify if it is a small spot (petechiae) or a raised lesion (ecchymoses or hematomas). Thereby, with accurate pathophysiology, diagnosis would be correct.⁷ 

There are different types of purpura, and the classification depends on the appearance or cause of the condition.

Non-thrombocytopenic purpura⁸

1. Platelet disorder: occurs due to the destruction of platelets.

• Idiopathic thrombocytopenic (primary) is typically caused by autoimmune or unknown reasons. It can also be caused by viral infections
• Secondary thrombocytopenic purpura is typically caused by external or internal factors such as drugs, infections, or systemic diseases, such as medication (heparin), infections (HIV or hepatitis C),  and systemic diseases including leukaemia or aplastic anaemia ⁹ 

2. Vascular: occurs when there is a leakage of blood through the vessel walls. 

It can be due to damage to small blood vessels or an increase in intraluminal pressure. Age or sun damage can also cause an impact.¹⁰ 

Causes of purpura 

Benign conditions

Benign conditions are non-cancerous growths in the body:⁴

1. Trauma or injury: small injuries or pressure applied to the blood vessels can result in the breakage of skin, which can progress into purpura
2. Medications: specific medications, such as blood thinners, including warfarin or aspirin, can increase the risk of bruising and purpura
3. Vitamin deficiencies: A deficiency in vitamin C or vitamin K can result in weakened blood vessels, contributing to purpura

Serious or life-threatening conditions¹¹

1. Coagulation disorders: disorders such as haemophilia or disseminated intravascular coagulation (DIC), where the blood’s ability to clot is impaired, can lead to purpura
2. Sepsis: A severe infection can cause widespread inflammation and clotting, potentially leading to purpura, especially if it results in disseminated intravascular coagulation (DIC)
3. Leukaemia or other blood cancers: certain blood cancers can lead to abnormalities in the platelet function or blood vessel integrity, causing purpura

Clinical history and physical examination 

An important part of diagnosing purpura is a thorough patient history and physical examination. This will enable the dermatologists to understand if there may be any underlying conditions or factors that may impact the cause of the condition occurring. It can also help with treatment options that are best suited for the patient. A detailed examination can also help dermatologists to differentiate purpura from other skin conditions.²⁶ 

Clinical history 

The first step during a clinical examination is to collect information on the condition itself, including the onset and duration from when the patient first noted the purpura. This will enable the dermatologist to understand if it is a vasculitic or immune-mediated process. However, gradual onsets suggest that it may be a systematic disorder such as coagulopathy.¹² 

This can then be confirmed by the symptoms present. Systematic symptoms include weight loss, fever, or malaise, which are common for conditions such as vasculitis or infections. Therefore, medications can be provided to the patient, such as anticoagulants (warfarin, heparin), antibiotics (penicillin), and immunosuppressants (corticosteroids).¹³ 

Examining the patient’s recent history of infections, whether bacterial or viral, as well as identifying any comorbidities such as chronic liver disease, kidney failure, or bleeding disorders, can help determine potential contributing factors to the condition.²⁷

Physical examination

Physical examination includes examining the size, shape, and distribution of lesions to help differentiate between petechiae and ecchymoses. This provides information on the cause of the condition. Furthermore, colour can also help with categorising. For instance, ecchymosis will change colour from red to purple, then green, and yellow over time. Lastly, systemic involvement is examined via signs of internal bleeding, such as joint pain or abdominal pain, which could indicate systemic vasculitis or coagulopathy.¹⁴

Distinguishing purpura from other skin conditions

It is important to differentiate other skin conditions from purpura because several skin conditions can present with purpura-like lesions.²⁵ Examples are:

1. Ecchymosis (Bruising)

The pathophysiology of ecchymosis involves a large skin haemorrhage caused by trauma to the blood vessels. It can be differentiated from purpura due to its occurrence. Purpura can form without direct trauma; however, ecchymosis is typically from a direct injury. 

Furthermore, ecchymosis follows a pattern of gradual colour changes as blood leaks and is reabsorbed.¹⁵

2. Petechiae

Petechiae can be identified and differentiated by their visual characteristics, such as size. Typically, they are small, less than 3 mm in diameter, and usually occur due to capillary rupture. Although they can be associated with purpura, they can also be an independent condition, such as thrombocytopenia.

They can be found in areas of higher pressure, for instance, the lower limbs or the mucous membrane.¹⁶ 

3. Erythema (Redness)

Erythema can be identified by inflammation or dilution around the area of the blood vessel in the skin. These symptoms are similar to purpura; therefore, they can be mistaken.¹⁷ 

4. Vasculitis

Vasculitis can be mistaken for purpura due to the inflammation of blood vessels surrounding the tissues. However, vasculitis can be detected alongside other systemic symptoms such as fever, weight loss, and organ involvement.¹⁸ 

5. Vascular malformations

Arteriovenous malformations (AVMs) and cavernous hemangiomas are two types of vascular malformations. They present as purple lesions that can be similar to purpura. However, vascular malformations typically appear from birth and enlarge with time. They can be found on the face or limbs and are not associated with bleeding or systemic illnesses like purpura.¹⁹ 

6. Dermatitis and other inflammatory skin conditions

Inflammatory conditions such as eczema, contact dermatitis, and drug eruptions can sometimes cause erythema or papular lesions that may appear similar to purpura. They are usually pruritic (itchy) and are typically identified through clinical history examinations. For instance, an allergic reaction or exposure to something. Skin lesions are usually more inflammatory in nature rather than the result of blood vessel leakage.²⁰

Laboratory investigations

It is important to conduct further laboratory investigations to help accurately diagnose purpura and to confirm any underlying causes. Tests can include:

1. Complete blood count (CBC)

CBC can be used to identify any platelet disorders, such as thrombocytopenia (low platelet count).

2. Coagulation studies

Prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen levels help to assess for coagulation disorders, such as disseminated intravascular coagulation (DIC) or haemophilia.²²

3. Antinuclear antibodies (ANA)

A positive ANA test may suggest an autoimmune condition such as systemic lupus erythematosus or vasculitis.²³

4. Skin biopsy

Skin biopsies can help understand the vascular involvement and presence of inflammation in vasculitis or other dermatological diseases.²⁴ 

Management and treatment

Treatment of purpura depends on the underlying causes:

• Idiopathic thrombocytopenic purpura (ITP) is treated with corticosteroids and immunoglobulin therapy
• Vasculitis: Treatment with corticosteroids or immunosuppressive drugs may be required
• Infectious causes: Antibiotics or antivirals may be necessary to treat underlying infections
• Coagulation disorders: Factor replacement therapy is indicated in conditions like haemophilia

Conclusion

Purpura is characterised by a red-brown lesion that is caused by localised haemorrhage under the skin. It can be mistaken for other skin conditions; therefore, it is important to differentiate purpura to ensure accurate diagnosis of the underlying cause and determine the appropriate treatment.²⁵ 

Carrying out a clinical history, physical examination, and targeted laboratory investigations can aid with identification and diagnosis. While many skin conditions can present with purpura-like lesions, understanding the distinguishing features of each disorder will enable clinicians to make an accurate diagnosis and provide the best possible care for patients.