science

Leser–Trélat sign

Leser–Trélat sign 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 Leser–Trélat sign rather than just read about it. In short: The Leser–Trélat sign is the explosive onset of multiple seborrheic keratoses (many pigmented skin lesions), often with an inflammatory base. This can be a sign of internal malignancy as part of a paraneoplastic syndrome.

Key takeaways

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

Reference excerpt

The Leser–Trélat sign is the explosive onset of multiple seborrheic keratoses (many pigmented skin lesions), often with an inflammatory base. This can be a sign of internal malignancy as part of a paraneoplastic syndrome. In addition to the development of new lesions, preexisting ones frequently increase in size and become symptomatic.

Associations Although most associated neoplasms are gastrointestinal adenocarcinomas (stomach, liver, colorectal and pancreas), malignancies of the breast, lung, and urinary tract, as well as lymphoid tissue, have been associated with this distinctive rash. It is likely that various cytokines and other growth factors produced by the neoplasm are responsible for the abrupt appearance of the seborrheic keratoses. In some cases, paraneoplastic acanthosis nigricans (35% of patients), florid cutaneous papillomatosis, ichthyosis acquisita (acquired hypertrichosis lanuginosa), Cowden syndrome, tylosis, acrokeratosis paraneoplastica of Bazex or tripe palms accompany the sign of Leser–Trélat.

History It is named for German surgeon Edmund Leser and French surgeon Ulysse Trélat. It has been suggested that Leser and Trélat were observing angiomas and not seborrheic keratoses, and so the credit should properly go to Eugen Von Hollander for his 1900 publication.

References

Illustrations

Worked examples

Example 1 — a first encounter with Leser–Trélat sign

Start with the simplest possible case. Write down what Leser–Trélat sign 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 Leser–Trélat sign 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 Leser–Trélat sign 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 Leser–Trélat sign

In research: Leser–Trélat sign 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 Leser–Trélat sign 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: Leser–Trélat sign is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dermatologic signs, Paraneoplastic syndromes, so understanding it makes those chapters shorter.
In everyday life: Look for Leser–Trélat sign 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 Leser–Trélat sign in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Leser–Trélat sign 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 Leser–Trélat sign out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Leser–Trélat sign in simple terms?

Why does Leser–Trélat sign 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 Leser–Trélat sign?

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 Leser–Trélat sign.