science

Purpura

Purpura is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Purpura rather than just read about it. In short: Purpura () is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, or other causes.

Key takeaways

Purpura belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Purpura to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Purpura from memory before moving on to harder problems.

Reference excerpt

Purpura () is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, or other causes. They measure 3–10 mm, whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm. Purpura is common with typhus and can be present with meningitis caused by meningococci or septicaemia. In particular, meningococcus (Neisseria meningitidis), a Gram-negative diplococcus organism, releases endotoxin when it lyses. Endotoxin activates the Hageman factor (clotting factor XII), which causes disseminated intravascular coagulation (DIC). The DIC is what appears as a rash on the affected individual.

Classification Purpura are a common and nonspecific medical sign; however, the underlying mechanism commonly involves one of:

Platelet disorders (thrombocytopenic purpura) Primary thrombocytopenic purpura Secondary thrombocytopenic purpura Post-transfusion purpura Vascular disorders (nonthrombocytopenic purpura) Microvascular injury, as seen in senile (old age) purpura, when blood vessels are more easily damaged Hypertensive states Deficient vascular support Vasculitis, as in the case of Henoch–Schönlein purpura Coagulation disorders Disseminated intravascular coagulation (DIC) Scurvy (vitamin C deficiency) – defect in collagen synthesis due to lack of hydroxylation of procollagen results in weakened capillary walls and cells Meningococcemia Clumping fibrillary protein deposits caused by Amyloidosis Cocaine use with concomitant use of the one-time chemotherapy drug and now veterinary deworming agent levamisole can cause purpura of the ears, face, trunk, or extremities, sometimes needing reconstructive surgery. Levamisole is purportedly a common cutting agent. Decomposition of blood vessels including purpura is a symptom of acute radiation poisoning in excess of 2 Grays of radiation exposure. This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster. Cases of psychogenic purpura are also described in the medical literature, some claimed to be due to "autoerythrocyte sensitization". Other studies suggest the local (cutaneous) activity of tissue plasminogen activator can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding. Petechial rash is also characteristic of a rickettsial infection.

Etymology and pronunciation The word purpura () comes from Latin purpura, "purple", which came from ancient Greek πορφύρα. Purpura is a mass noun naming the condition or state, not the name of an individual spot (thus there is no *purpurum, *purpura or *purpura, *purpurae count declension).

See also Bruise, which is a hematoma caused by trauma Purpura secondary to clotting disorders Purpura hemorrhagica in horses Pigmented purpuric dermatosis Schamberg disease (progressive pigmentary purpura)

References

External links

Evaluating the Child with Purpura Archived 2008-10-16 at the Wayback Machine from American Academy of Family Physicians

Illustrations

Worked examples

Example 1 — a first encounter with Purpura

Start with the simplest possible case. Write down what Purpura claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Purpura before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Purpura ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Purpura

In research: Purpura appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Purpura in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Purpura is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dermatologic terminology, Medical signs, so understanding it makes those chapters shorter.
In everyday life: Look for Purpura outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Purpura in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Purpura means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Purpura out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Purpura in simple terms?

Why does Purpura matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Purpura?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Purpura.