Purpura is the appearance of red or purple discolorations on the skin that do not blanch upon applying pressure. They are 3-10mm in size, whereas petechiae are less than 3mm, and ecchymoses are greater than 1cm.

Blueberry muffin baby is the characteristic distributed purpura that occurs as a result of extramedullary hematopoiesis found in infants. The purpura is often generalized but favors the trunk, head, and neck.

Cryofibrinogenemic purpura is a painful purpura that affects both feet in the winter months, causing slow healing ulcerations and edema.

Cryoglobulinemic purpura occurs most frequently in multiple myeloma and macroglobulinemia.

Degos disease (also called malignant atrophic papulosis) affects the lining of the medium and small veins and arteries, resulting in occlusion (blockage of the vessel) and tissue infarction. It affects the blood vessels that supply the skin, gastrointestinal tract and central nervous system and can result in bowel ischemia (mesenteric ischemia or ischemic colitis), chronic skin lesions, ocular lesions, strokes, spinal lesions, mononeuritis multiplex, epilepsy, headaches or cognitive disorders. Pleural or pericardial effusions are also reported.There are fewer than 50 living patients at present known worldwide, and fewer than 200 reported in medical literature.

Doucas and Kapetanakis pigmented purpura (also known as eczematoid purpura or eczematoid-like purpura) is characterized by scaly and eczematous patches, which also have petechiae and hemosiderin staining.

Drug-induced thrombocytopenic purpura is the result of anti-platelet antibodies caused by drugs such as heparin, sulfonamines, digoxin, quinine and quinidine.

Gougerot–Blum syndrome (also known as pigmented purpuric lichenoid dermatitis and pigmented purpuric lichenoid dermatitis of Gougerot and Blum) is a variant of pigmented purpuric dermatitis, a skin condition characterized by minute, rust-colored to violet, lichenoid papules that tend to fuse into plaques of various hues.

Henoch–Schönlein purpura (also known as anaphylactoid purpura, purpura rheumatica and Schönlein–Henoch purpura) is a systemic vasculitis (inflammation of blood vessels) and is characterized by deposition of immune complexes containing the antibody IgA. HSP occurs more often in children than in adults (half of its affected patients are under the age of six and 90% are under ten) and usually follows an upper respiratory tract infection. Its exact cause is unknown, though it usually resolves within several weeks.

Purpura, arthritis and abdominal pain are known as the ‘classic triad’ of HSP. Purpura occurs in all cases, joint pains and arthritis in 80%, and abdominal pain in 62%. Some include gastrointestinal hemorrhage as a fourth criterion; this occurs in 33% of cases, sometimes, but not necessarily always, due to intussusception.

Typically, the purpura appears on the legs and buttocks, but may also be seen on the arms, face and trunk. The abdominal pain is colicky in character, and may be accompanied by nausea, vomiting, constipation or diarrhea, and there may be blood or mucus in the stool. The joints involved tend to be the ankles, knees and elbows, but arthritis in the hands and feet is possible; the arthritis is nonerosive and causes no permanent deformity. Forty percent of affected individuals have evidence of kidney involvement, mainly in the form of hematuria (blood in the urine). Problems in other organs, such as the central nervous system (brain and spinal cord) and lungs may occur, but these are much less common than in the skin, bowel and kidneys.

Idiopathic thrombocytopenic purpura (also known primary immune thrombocytopenia, primary immune thrombocytopenic purpura and autoimmune thrombocytopenic purpura) is defined as isolated low platelet count (thrombocytopenia) with normal bone marrow and the absence of other causes of thrombocytopenia. It causes a characteristic purpuric rash and an increased tendency to bleed 

Symptoms of ITP include the spontaneous formation of purpura and petechiae (especially on the extremities) bleeding from the nostrils and/or gums, and menorrhagia (excessive menstrual bleeding), any of which may occur if the platelet count is below 20,000 per microlitre (μl). A normal platelet count is considered to be in the range of 150,000–450,000 per μl of blood for most healthy individuals. A very low count (less than 10,000 per μl) may result in the spontaneous formation of hematomas (blood masses) in the mouth or on other mucous membranes. Bleeding time from minor cuts or scratching is usually prolonged.

Two distinct clinical syndromes manifest as an acute condition in children and a chronic condition in adults. The acute form often follows an infection and has a spontaneous resolution within 2 months. Chronic idiopathic thrombocytopenic purpura persists longer than six months, without a specific cause.

Acute hemorrhagic edema of infancy (also known as acute hemorrhagic edema of childhood, Finkelstein's disease, infantile postinfectious iris-like purpura and edema, medallion-like purpura, purpura en cocarde avec oedema and Seidlmayer syndrome) affects children under the age of two that have had a recent history of upper respiratory illness, a course of antibiotics, or both.

Majocchi's disease (also known as purpura annularis telangiectodes and purpura annularis telangiectodes of Majocchi) is a skin condition characterized by bluish-red 1- to 3-cm patches composed of dark red telangiectases with petechiae.

Obstructive purpura is a skin condition that may result from mechanical obstruction to circulation, with resulting stress on the small vessels leading to purpura.

Orthostatic purpura (also known as stasis purpura) is the result of prolonged standing or even sitting with the legs lowered (as in a bus, airplane, or train), which produces edema and a purpuric eruption on the lower extremities.

Painful bruising syndrome (also known as autoerythrocyte sensitization, Gardner–Diamond syndrome and psychogenic purpura) is a rare, idiopathic trauma-induced condition seen in young to middle-aged women. It’s characterized by a distinctive localized purpuric reaction that primarily occurs on the legs, face and trunk. It also has painful recurring ecchymoses that are variably accompanied by syncope (passing out from a drop in blood pressure), nausea, vomiting, gastrointestinal and intracranial bleeding.

Purpuric agave dermatitis is caused by Agave americana (a large, thick, long-leaved, subtropical plant).

Purpura fulminans (also known as purpura gangrenosa) is an acute, often fatal, thrombotic disorder which manifests as blood spots, bruising and discoloration of the skin. It is rare and mainly occurs in babies and small children, though it may manifest in adults when associated with severe infections.

Purpura fulminans is caused by defects in the protein C anticoagulant pathway. Identification of the cause of purpura fulminans often depends on the patient’s age and the circumstances of its presentation. It may be congenital, acquired, a feature of severe acute sepsis, idiopathic, or a combination of these.

The initial appearance of purpura fulminans lesions is that of well-demarcated erythematous lesions which progress rapidly to develop irregular central areas of blue-black haemorrhagic necrosis. Advancing areas of necrosis are often surrounded by a thin border of erythema that fades into the adjacent unaffected skin. Haemorrhage into the necrotic skin causes purpura fulminans lesions to become painful, dark and raised, sometimes with vesicle or blister formation.

The distribution of purpura fulminans lesions may be different according to the underlying pathogenesis. Purpura fulminans in severe sepsis typically develops in the distal extremities and progresses proximally or appears as a generalized or diffuse rash affecting the whole body surface. In cases of severe inheritable protein C deficiency, purpura fulminans with disseminated intravascular coagulation manifests within a few hours or days after birth.

Purpura fulminans lesions, once established, often progress within 24 to 48 hours to full-thickness skin necrosis or soft-tissue necrosis. Once the purpura fulminans lesions have progressed to this point, it takes between 4-8 weeks for them to heal and they leave behind large scars.

Without treatment, necrotic soft tissue may become gangrenous, leading to loss of limbs. Purpura fulminans is often accompanied by micro-vascular thrombosis and haemorrhagic infarction in other tissues (such as the lungs, kidneys, central nervous system and adrenal glands) leading to multiple organ failure. Purpura fulminans may also lead to severe large vessel venous thrombosis if untreated in its early stages.

Purpura secondary to clotting disorders occur due to hereditary disorders of blood coagulation, such as in hemophilia or von Willebrand's disease.

Solar purpura (also known as actinic purpura and senile purpura) is a skin condition characterized by large, sharply outlined, 1 to 5cm, dark purplish-red ecchymoses appearing on the upper region of the forearms and hands. This condition is most common in elderly white individuals and is caused by sun-induced damage to the connective tissue of the skin. The lesions typically fade over a period of up to 3 weeks.