You might sometimes see purple spots or patches on your skin and wonder what that might be. Most of the time, they are harmless and disappear on their own, but sometimes they can indicate a serious condition. What are these patches, and what do they do? 

What is purpura?

Purpura is a skin sign that causes small, flat purple spots or patches to appear on the skin or the mucous membranes. The colour of these patches depends on the colour of your skin, which means that they might appear reddish-purple on lighter skin tones and brownish-black on darker skin tones. It may also look like a bruise or a spot of blood under the skin. Purpura occurs when small blood vessels leak under the skin's surface, and it’s not a medical condition but a sign of a condition. Purpura can appear anywhere on the skin, especially on the arms, hands, feet, and legs.

Types of purpura

There are two main types of purpura:

• Thrombocytopenic purpura: occurs when a person has low platelet counts
• Non-thrombocytopenic purpura: occurs in people with a normal platelet count, and there is another reason behind the purpura

Thrombocytopenic purpura

There are three types of thrombocytopenic purpura:

• Thrombotic thrombocytopenic purpura
• Immune thrombocytopenic purpura
• Drug-induced thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP)

TTP is characterised by:

• Microangiopathic hemolytic anaemia (MAHA) 
• Severe thrombocytopenia
• Variable organ ischemia (mostly neurologic, cardiac, or renal) 

The cause of TTP is the deficiency of a specific enzyme, which leads to a disturbance in the coagulation system in the body through the accumulation of a specific coagulation factor that causes the formation of platelet-rich microthrombi in the small arterioles. TTP can be induced by some conditions, such as pregnancy, some autoimmune diseases, HIV, cancer, and organ transplantation.² 

TTP is divided into two categories:^{1 2} 

• Congenital (inherited) 
• Immune-mediated (Acquired)

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) usually presents in adults (90% of cases), and people assigned female at birth are 2-3 times more likely to develop iTTP than people assigned male at birth.¹

Clinical presentations of TTP 

• Hemolytic anaemia
• Headaches
• Dizziness
• Slurred speech 
• Serious symptoms like amaurosis, agitation to stroke, epileptic seizures, or coma
• Renal: increased serum creatinine, oligo or anuria, and hemolysis-induced hemoglobinuria. Hemolysis can sometimes cause jaundice and signs of anaemia as well
• Cardiac: increase in cardiac enzymes, myocardial hypoperfusion/infarction, or arrhythmia, and the development of cardiac failure is a serious complication that might lead to immediate death. 
• Other organs involved might include the lungs (gas exchange problems or lung infiltrate), pancreas (like diabetes), and gastrointestinal tract.³

A condition such as TTP requires urgent management, and the treatment options include plasma exchange therapy (replacing the patient’s plasma with a donor’s plasma, which improved survival from about 10 to 80--90%), plasma infusion (usually for congenital cases), immunosuppression (like steroids and other drugs), and supportive care.³

Immune thrombocytopenic purpura (ITP)

The most likely cause of this condition is that the patients develop autoantibodies against platelet membrane proteins, which, in the end, inhibit platelet normal destruction, and therefore, thrombocytopenia.⁴

About 12 of 100.000 adults develop ITP every year. People assigned females at birth are more susceptible to having it because of the oestrogen that can promote autoimmunity.⁴

ITP is divided into: 

• Primary – acquired ITP
• Secondary – triggered by another disorder or medicine

Some of these disorders are autoimmune diseases (such as lupus, and rheumatoid arthritis), endocrine disorders (such as hypothyroidism, and Adison’s diseases), chronic infections (HIV, hepatitis C), and lymphatic neoplasms (such as lymphoma and chronic lymphocytic leukaemia).⁵ Some medications that can cause ITP are heparin, beta-lactam antibiotics, vancomycin, gold compounds, and other antibiotics and medications.⁴

The symptoms depend on the severity of the case, and the most serious sign is bleeding, which also depends on the platelet count and can range from mild to severe, such as cutaneous and mucosal bleeding, and, in severe cases, it might be intracranial, intestinal, or any other internal bleeding. It’s important to know that many ITP patients are asymptomatic. Another type of bleeding might be oral or nasal, which might also be mild or severe. Although severe bleeding is rare in ITP, it’s dangerous and can be fatal. Other symptoms might include fatigue or thrombosis.⁵

The treatment depends on whether ITP is primary or secondary. However, the critical management in both types is to stop the bleeding. In secondary cases, it’s essential to treat the underlying condition or discontinue the causing medicine. The therapeutic procedures include platelet transfusion (only in critical bleeding because it’s the fastest way to increase the platelet count), corticosteroids, IVIG, and other therapies.⁵

Drug-induced thrombocytopenic purpura

Drug-induced thrombocytopenia occurs when certain medications destroy the platelets or decrease the ability of the body to make enough of them. There are two types, immune (the medicine causes the body to produce antibodies that destroy the platelets) and nonimmune (the medicine prevents the bone marrow from producing enough platelets). 

The most common medications that cause this condition are chemotherapy drugs and valproic acid (seizure medicine). Other medications include furosemide, nonsteroidal anti-inflammatory drugs (NSAIDs), penicillin, statins, and others. 

The symptoms include abnormal bleeding, easy bruising, and red spots on the skin. The first step of the treatment is to stop the inducing medicine, and for patients with life-threatening bleeding, the therapies include plasma exchange, platelet transfusions, corticosteroids, and intravenous immunoglobulin.

Non-thrombocytopenic purpura

It includes two types:

• Henoch-Schonlein purpura
• Coagulation-associated purpura

Henoch-Schonlein Purpura (HSP)

• It’s a small-vessel vasculitis, and it’s more common in children (90% of cases) and it’s often self-limited. However, this condition in adults is more severe, with several complications (3.4--14.3 cases per million).⁶
• Many factors can trigger this condition, such as infections (like group A Streptococcus, Methicillin-resistant Staphylococcus aureus, Helicobacter pylori, Parvovirus B19, Hepatitis B, Human Immunodeficiency Virus, and Stenotrophomonas maltophilia), some allergens, such as some medicines and antigens associated with malignancy, and some autoimmune disorders.⁶

The manifestations of this condition in adults include:⁶

• Skin – It is the most involved site, which starts with lesions and evolves into palpable purpura with symmetrical distribution on the extremities and trunk. In 35% of cases, blistering and hemorrhagic necrotic skin lesions might occur. 
• Joints – Arthritis is the second most common manifestation, occurring in 61% of cases
• Gastrointestinal – Involvement occurs in 48% of cases (mostly colicky pain or ulcer bleeding, usually from the second part of the duodenum, ileum, or rectum). The most
• Kidney – Renal impairment is one of the serious complications (45--85% of cases), and the most common manifestation is glomerulonephritis.
•  Other unusual complications include pulmonary involvement, cardiac involvement, scrotal pain, central or peripheral nervous system involvement, and seizures.⁶

The treatment of HSP depends on the severity of the case. In mild cases, NSAIDs can be enough. In severe skin lesions, the most appropriate medicine is colchicine. Other treatments include sulfones, corticosteroids, and others.⁶

Coagulation-associated purpura

This type is called purpura fulminans (PF), and it’s uncommon. This condition is life-threatening and rapidly progressive. It’s an unusual type of disseminated intravascular coagulation (DIC) and is characterised by small vessel thrombosis and hemorrhagic skin necrosis. It typically starts with well-demarcated macules that develop central hemorrhagic necrosis and progress to purpura, and it sometimes might result in gangrene. When there is a septic shock, it usually affects the extremities as a result of poor blood perfusion to these parts. Purpura fulminans are classified into three types: neonatal PF, acute infectious PF (the most common), and idiopathic PF (usually post-infection).⁷ 

Purpura diagnosis

The most important thing is to determine the underlying cause of purpura.

• Skin examination (colour and size of purpura) and, sometimes, skin biopsy.
• Medical and drug history.
• Complete blood count (CBC).
• A blood test (to see if the underlying condition is a coagulation disorder or platelet-related). 

FAQs

Is purpura dangerous?

Usually, purpura in itself isn’t a condition, but the condition that could’ve caused it might be dangerous. However, there are some conditions where purpura is considered a life-threatening condition and requires immediate management.

Is purpura painful?

Purpuric rash usually doesn’t hurt or itch, yet some people who feel the skin, where the purpura is, is tender or more sensitive.

Is petechiae the same as purpura?

Purpura is usually 4-10 mm in diameter, while petechiae are less than 4 mm wide and are dot-like.

Summary

Purpura is mostly a simple, self-limiting symptom of underlying conditions or drugs. However, it can be a serious and life-threatening condition by itself. Therefore, it’s highly recommended to ask your doctor about any sudden bruise-like patches or any changes in your skin in general because they might indicate a dangerous disorder that requires immediate management.