Oculopharyngeal muscular dystrophy
Encyclopedia
Oculopharyngeal muscular dystrophy (OPMD) is an autosomal
dominant neuromuscular disease
which appears in early middle age
(sixth decade). OPMD is an example of a trinucleotide repeat disorder caused by expanding (GCN)10 to (GCN)11-17 at the 5' end of the coding region for PABPN1
. This expands the polyalanine tract at the N-terminus of PABPN1
from 10 to 11-17 alanines
.
(drooping of eyelids)and weakness of the extraocular muscles is the initial clinical finding which continues until paralysis of all eye movements occurs; however, pupillary reactions remain unaffected. Dysphagia
(difficulty swallowing), facial weakness and proximal limb weakness develops later on in the disease.
reveals abnormal vacuoles within muscle fibres. A distinction between OPMD and myasthenia gravis
or mitochondrial myopathy
must be made. The absence of family history and the fluctuation of symptoms in myasthenia gravis usually distinguish the two conditions.
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
dominant neuromuscular disease
Muscular dystrophy
Muscular dystrophy is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.In the 1860s, descriptions of boys who...
which appears in early middle age
Middle age
Middle age is the period of age beyond young adulthood but before the onset of old age. Various attempts have been made to define this age, which is around the third quarter of the average life span of human beings....
(sixth decade). OPMD is an example of a trinucleotide repeat disorder caused by expanding (GCN)10 to (GCN)11-17 at the 5' end of the coding region for PABPN1
PABPN1
Polyadenylate-binding protein 2 also known as polyadenylate-binding nuclear protein 1 is a protein that in humans is encoded by the PABPN1 gene.- Function :...
. This expands the polyalanine tract at the N-terminus of PABPN1
PABPN1
Polyadenylate-binding protein 2 also known as polyadenylate-binding nuclear protein 1 is a protein that in humans is encoded by the PABPN1 gene.- Function :...
from 10 to 11-17 alanines
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
.
Signs and symptoms
Progressive ptosisPtosis
Ptosis refers to droopiness of a body part. Specifically, it can refer to:* Ptosis * Ptosis * Enteroptosis * Gastroptosis...
(drooping of eyelids)and weakness of the extraocular muscles is the initial clinical finding which continues until paralysis of all eye movements occurs; however, pupillary reactions remain unaffected. Dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
(difficulty swallowing), facial weakness and proximal limb weakness develops later on in the disease.
Diagnosis
A muscle biopsyMuscle biopsy
In medicine, a muscle biopsy is a procedure in which a piece of muscle tissue is removed from an organism and examined microscopically. A biopsy needle is usually inserted into a muscle, wherein a small amount of tissue remains. Alternatively, an "open biopsy" can be performed by obtaining the...
reveals abnormal vacuoles within muscle fibres. A distinction between OPMD and myasthenia gravis
Myasthenia gravis
Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...
or mitochondrial myopathy
Mitochondrial myopathy
Mitochondrial myopathy is a type of myopathy associated with mitochondrial disease. On biopsy, the muscle tissue of patients with this disease usually demonstrate "ragged red" muscle fibers...
must be made. The absence of family history and the fluctuation of symptoms in myasthenia gravis usually distinguish the two conditions.