biology

Oculopharyngodistal myopathy

Oculopharyngodistal myopathy is a biology 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 Oculopharyngodistal myopathy rather than just read about it. In short: Oculopharyngodistal myopathy is a rare genetic disorder characterized by progressive muscle weakness affecting various parts of the body. Signs and symptoms People with this condition exhibit symptoms susch as progressive muscle weakness affecting the eyes, face, and pharynx which consequently results in blepharoptosis, ophthalmoparesis, atrophy of the facial muscles, dysphagia, dysarthria, and muscle weakness and a…

Key takeaways

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Connect Oculopharyngodistal myopathy to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Oculopharyngodistal myopathy from memory before moving on to harder problems.

Reference excerpt

Oculopharyngodistal myopathy is a rare genetic disorder characterized by progressive muscle weakness affecting various parts of the body.

Signs and symptoms People with this condition exhibit symptoms susch as progressive muscle weakness affecting the eyes, face, and pharynx which consequently results in blepharoptosis, ophthalmoparesis, atrophy of the facial muscles, dysphagia, dysarthria, and muscle weakness and atrophy of the upper and lower distal limbs. These symptoms usually start during adulthood. On rare cases, hearing loss, severe proximal weakness and/or unilateral muscle weakness.

Complications Complications vary depending on the symptoms and their severity, for example, muscle weakness might leave people unable to work on manual labor jobs.

Diagnosis This condition can be diagnosed through physical examination and sequencing of the genes associated with the condition.

Genetics There are four known genetic causes of this disorder: 1. Trinucleotide repeat expansion located in the 5-prime untranslated region of the LRP12 gene. (CGG) 2. Trinucleotide repeat expansion located in the 5-prime untranslated region of the G1PC gene. (GGC) 3. Trinucleotide repeat expansion located in the non-coding region of the NOTCH2NLC gene. (CGG) 4. Trinucleotide repeat expansion located in the 5-prime untranslated region of the RILPL1 gene. All of these mutations are inherited/expressed in an autosomal dominant manner, meaning that for a person to exhibit the symptoms of this condition, they must inherit a copy of the mutated allele from at least one parent, although in other cases, the mutation might not have been inherited, but rather the result of a spontaneous error.

Prevalence According to three OMIM pages for this condition, about 78 families across the world are known to have this condition, this includes both familial and sporadic cases with confirmed genetic basis (thus, potential to spread to offspring and turn it into a familial case). Most (if not all) of these families are of East Asian (Japanese and Chinese in particular) descent. OMIM divided this condition into subtypes due to the different genetic causes and slightly different symptoms the three of them exhibit. The following list comprises the number of families described in medical literature each of these subtypes has:

# 164310 OCULOPHARYNGODISTAL MYOPATHY 1; OPDM1: 37 families

# 618940 OCULOPHARYNGODISTAL MYOPATHY 2; OPDM2: 30 families

# 619473 OCULOPHARYNGODISTAL MYOPATHY 3; OPDM3: 11 families.

History This condition was first discovered in 1977 by E Sayotoshi et al. when they described an unspecified number of people from four families who suffered from an "autosomal dominant, heredofamilial myopathy" which consisted in "slowly progressive ptosis and extraocular palsy, and weakness of the masseter, facial, and bulbar muscles, as well as distal involvement of the limbs starting around 40 years of age or later." In 2019, Hiroyuki Ishiura et al. discovered a heterozygous trinucleotide repeat expansion in the 5-prime untranslated region of the LRP12 gene in 5 patients with the condition, the trinucleotide sequence consisted of one C (cytosine) and two Gs (guanine). By using Southern blot analysis of leukocytes, it was revealed that the patients (on average) had expanded repeats ranging from 280 to 380 bp which was the equivalent of more than 90 repeats of CGG, when the LRP12 gene of 1,000 control subjects was tested with the same method, it was revealed that they (on average) had between 13 and 45 repeat units of the same nucleotides, with the exception of two out of the 1,000 controls, who had expanded repeats without any symptoms of the condition. In 2020, Deng et al. discovered heterozygous trinucleotide repeat expansions in the 5-prime untranslated region of the GIPC1 gene of multiple affected members from three Chinese families, this trinucleotide sequence consisted of two Gs (guanine) and one C (cytosine). This mutation was later identified by the same team of researchers in 16 patients, of which 9 were Chinese and 7 were Japanese. In 2020, Ogasawara et al. discovered heterozygous trinucleotide repeat expansions in the non-coding region of the NOTCH2NLC gene of seven un-related Japanese patients with the condition, the trinucleotide sequence consisted of one C (cytosine) and two Gs (guanine), all five patients had more than 100 repeats of the trinucleotide sequence, one of which had two expansions consisting of 217 and 674 repeats.

See also Myopathy Familial episodic pain syndrome

References

Illustrations

Worked examples

Example 1 — a first encounter with Oculopharyngodistal myopathy

Start with the simplest possible case. Write down what Oculopharyngodistal myopathy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Oculopharyngodistal myopathy 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 Oculopharyngodistal myopathy 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 Oculopharyngodistal myopathy

In research: Oculopharyngodistal myopathy appears in biology 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 Oculopharyngodistal myopathy 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: Oculopharyngodistal myopathy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genetic diseases and disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Oculopharyngodistal myopathy 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 Oculopharyngodistal myopathy in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Oculopharyngodistal myopathy means in your own words.
Compare your version with the excerpt and mark what you missed.
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Frequently asked questions

What is Oculopharyngodistal myopathy in simple terms?

Oculopharyngodistal myopathy is a rare genetic disorder characterized by progressive muscle weakness affecting various parts of the body. Signs and symptoms People with this condition exhibit symptoms susch as progressive muscle weakness affecting the eyes, face, and pharynx which consequently resu…

Why does Oculopharyngodistal myopathy matter?

Because it connects several biology 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 Oculopharyngodistal myopathy?

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 Oculopharyngodistal myopathy.