chemistry

Sjögren–Larsson syndrome

Sjögren–Larsson syndrome is a chemistry 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 Sjögren–Larsson syndrome rather than just read about it. In short: Sjögren–Larsson syndrome is a rare autosomal recessive form of ichthyosis with neurological symptoms. It can be identified by a triad of medical disorders.

Key takeaways

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

Reference excerpt

Sjögren–Larsson syndrome is a rare autosomal recessive form of ichthyosis with neurological symptoms. It can be identified by a triad of medical disorders. The first is ichthyosis, which is a buildup of skin to form a scale-like covering that causes dry skin and other problems. The second identifier is paraplegia which is characterized by leg spasms. The final identifier is intellectual delay. SLS is caused by a mutation in the fatty aldehyde dehydrogenase gene found on chromosome 17. In order for a child to receive SLS both parents must be carriers of the SLS gene. If they are carriers their child has a ⁠1/4⁠ chance of getting the disease. In 1957 Sjögren and Larsson proposed that the Swedes with the disease all descended from a common ancestor 600 years ago. Today only 30–40 persons in Sweden have this disease.

Signs and symptoms

Dry and scaly skin similar to all other ichtyosiforms (types of ichthyosis). Neurological problems – this can often cause mild paralysis in the legs Mild to moderate intellectual disability. Often associated ocular features, which include pigmentary changes in the retina. The usual presentation of crystalline maculopathy is from the age of 1–2 years onwards.

Causes It is associated with a deficiency of the enzyme fatty aldehyde dehydrogenase (ALDH3A2) which is encoded on the short arm of chromosome 17 (17p11.2). At least 11 distinct mutations have been identified. Without a functioning fatty aldehyde dehydrogenase enzyme, the body is unable to break down medium- and long-chain fatty aldehydes which then build up in the membranes of the skin and brain. A major source of these aldehydes is alpha oxidation. This condition is inherited in an autosomal recessive pattern.

Diagnosis Diagnosis is made with a blood test which sees if the activity of the fatty aldehyde dehydrogenase enzyme is normal. Gene sequencing can also be used, which can additionally be used by would-be parents to see if they are carriers.

Treatment The ichthyosis is usually treated with topical ointment. Anti-convulsants are used to treat seizures and the spasms may be improved with surgery.

Eponym It was characterized by Torsten Sjögren and Tage Konrad Leopold Larsson (1905–1998), a Swedish medical statistician. It should not be confused with Sjögren's syndrome, which is a distinct condition named after a different person, Henrik Sjögren.

See also Shabbir syndrome List of cutaneous conditions

References

Further reading Sjögren, K. G. Torsten; Larsson, Tage K. (1957). "Oligophrenia in combination with congenital ichtyosis and spastic disorders; a clinical and genetic study". Acta Psychiatrica Scandinavica. 32 (supplement 113). Copenhagen: 9–105. doi:10.1111/j.1600-0447.1956.tb04725.x. PMID 13457946. S2CID 72058188.

External links

Illustrations

Worked examples

Example 1 — a first encounter with Sjögren–Larsson syndrome

Start with the simplest possible case. Write down what Sjögren–Larsson syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Sjögren–Larsson syndrome 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 Sjögren–Larsson syndrome 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 Sjögren–Larsson syndrome

In research: Sjögren–Larsson syndrome appears in chemistry 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 Sjögren–Larsson syndrome 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: Sjögren–Larsson syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fatty-acid metabolism disorders, Genodermatoses, Rare diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Sjögren–Larsson syndrome 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 Sjögren–Larsson syndrome in 20 minutes

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

Frequently asked questions

What is Sjögren–Larsson syndrome in simple terms?

Sjögren–Larsson syndrome is a rare autosomal recessive form of ichthyosis with neurological symptoms. It can be identified by a triad of medical disorders.

Why does Sjögren–Larsson syndrome matter?

Because it connects several chemistry 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 Sjögren–Larsson syndrome?

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 Sjögren–Larsson syndrome.