Myoclonic dystonia
Encyclopedia
Myoclonic distonia or Myoclonus-dystonia syndrome is a rare syndrome having several subforms each traced to a different gene. The uniting feature is dystonia
, but there are also rapid jerky movements resembling myoclonus
.
Ethanol often ameliorates the symptoms very well, and so the syndrome is also called "Alcohol-responsive dystonia"; alcohol may be substituted by benzodiazepine
s that work through the same mechanism, such as clonazepam
.
Myoclonus Dystonia is in most cases caused by loss-of-function-mutations in the epsilon sarcoglycan
gene (SGCE
). The disease is dominantly inherited: there is a 50% chance that a child will inherit the mutation
if one parent has it. However, SGCE is an imprinted gene, and in fact only the paternal allele
is expressed. That is, only children who inherit the mutation from the father
will actually suffer from the disease. If the mutated allele is inherited from the mother
, the child will most probably stay healthy.
Dystonia
Dystonia is a neurological movement disorder, in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The disorder may be hereditary or caused by other factors such as birth-related or other physical trauma, infection, poisoning or reaction to...
, but there are also rapid jerky movements resembling myoclonus
Myoclonus
Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...
.
Ethanol often ameliorates the symptoms very well, and so the syndrome is also called "Alcohol-responsive dystonia"; alcohol may be substituted by benzodiazepine
Benzodiazepine
A benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...
s that work through the same mechanism, such as clonazepam
Clonazepam
Clonazepamis a benzodiazepine drug having anxiolytic, anticonvulsant, muscle relaxant, and hypnotic properties. It is marketed by Roche under the trade name Klonopin in the United States and Rivotril in Australia, Brazil, Canada and Europe...
.
Myoclonus Dystonia is in most cases caused by loss-of-function-mutations in the epsilon sarcoglycan
Sarcoglycan
The sarcoglycans are a family of transmembrane proteins involved in the protein complex responsible for connecting the muscle fibre cytoskeleton to the extracellular matrix, preventing damage to the muscle fibre sarcolemma through shearing forces.The dystrophin glycoprotein complex is a...
gene (SGCE
SGCE
Epsilon-sarcoglycan is a protein that in humans is encoded by the SGCE gene.-External links:*-External links:* LOVD mutation database:...
). The disease is dominantly inherited: there is a 50% chance that a child will inherit the mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
if one parent has it. However, SGCE is an imprinted gene, and in fact only the paternal allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
is expressed. That is, only children who inherit the mutation from the father
Father
A father, Pop, Dad, or Papa, is defined as a male parent of any type of offspring. The adjective "paternal" refers to father, parallel to "maternal" for mother...
will actually suffer from the disease. If the mutated allele is inherited from the mother
Mother
A mother, mum, mom, momma, or mama is a woman who has raised a child, given birth to a child, and/or supplied the ovum that grew into a child. Because of the complexity and differences of a mother's social, cultural, and religious definitions and roles, it is challenging to specify a universally...
, the child will most probably stay healthy.