Oculopharyngodistal myopathy
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| Oculopharyngodistal myopathy | |
|---|---|
 | |
| Specialty | Medical genetics |
| Symptoms | widespread muscle weakness and atrophy alongside other symptoms such as tremors and gait instability |
| Usual onset | adulthood (or near that period of time) |
| Duration | lifelong |
| Causes | genetic mutation |
| Risk factors | being of East Asian descent |
| Prevention | none |
| Frequency | rare, approximately 78 families are known to carry the gene for this condition |
| Deaths | - |
Oculopharyngodistal myopathy is a rare genetic disorder characterized by progressive muscle weakness affecting various parts of the body.
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.[1][2][3]
On rare cases, hearing loss, severe proximal weakness and/or unilateral muscle weakness.[1][2]
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)[4][5]
2. Trinucleotide repeat expansion located in the 5-prime untranslated region of the G1PC gene. (GGC)[4][5]
3. Trinucleotide repeat expansion located in the non-coding region of the NOTCH2NLC gene. (CGG)[4][5]
4. Trinucleotide repeat expansion located in the 5-prime untranslated region of the RILPL1 gene.[5]
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.[6]
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[7]
- # 618940
OCULOPHARYNGODISTAL MYOPATHY 2; OPDM2: 30 families[8]
- # 619473
OCULOPHARYNGODISTAL MYOPATHY 3; OPDM3: 11 families.[9]