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Dentatorubral-pallidoluysian atrophy (DRPLA) is a disorder of ataxia (loss of balance), choreoathetosis (involuntary rapid, irregular, jerky movements or slow, writhing movements that flow into one another), and dementia (inability to clearly think; confusion, poor judgement; failure to recognize people, places, and things; personality changes) in adults, and ataxia, myoclonus (involuntary spasms of a muscle or muscle group), epilepsy (seizures), and loss of intellectual function (mental retardation) in children.
DRPLA has also been referred to as Haw River syndrome and Natito-Oyanagi disease. The typical age of onset of DRPLA is 30, but it can present in people as young as one year of age and as late as 62 years of age, with differences in presentation between children and adults. In patients under the age of 20, DRPLA presents as seizures, ataxia, myoclonus, as well as progressive (worsening) mental deterioration. In patients over the age of 20, DRPLA is suspected when a person develops ataxia, choreoathetosis, dementia, and psychiatric disturbances (delusions, hallucinations). A positive family history (a relative with similar symptoms or one already diagnosed) confirms the diagnosis. DRPLA is sometimes initially thought to be Huntington disease.
A possible diagnosis of DRPLA can be devastating for a family to experience—their once healthy child, or young adult, will begin to have seizures, involuntary movements, loss of control over voluntary movement, and delusions—perhaps no longer being able to identify family members. Diagnosing DRPLA is complicated and requires a knowledgeable physician with expertise in both neurology and genetics. Usually an individual diagnosed with DRPLA already has a parent with the disease, however, if the disorder was not diagnosed properly, or the parent died prior to the onset of symptoms, or the parent has very late onset of the disease, there may not be a documented family history of DRPLA.
DRPLA is an autosomal dominant condition which means that both males and females are equally likely to have the disease, and an individual with the variant gene has a 50/50 chance to pass the condition to any child. The DRPLA gene is located on chromosome number 12 and has a section of DNA where the DNA alphabet is repeated in triplets, called CAG repeats. Normally a person has 6 to 35 CAG repeats in the DRPLA gene. In patients with DRPLA, there are 49 to 88 repeats which causes the gene's protein product, Atrophin 1, to be toxic to cells. Although scientists do not understand the exact mechanism, the number of repeats expands when the gene is transmitted from parent to child. The size of the repeat transmitted to the next generation depends upon the size of the parent's repeat and the sex of the transmitting parent.
There is an inverse correlation between the age of onset and the size of the expanded CAG repeats. In other words, the younger the age of onset, the larger the number of CAG repeats:
DRPLA as well as other genetic conditions, exhibits a phenomenon known as anticipation. Anticipation means that the disease increases in severity and presents at a younger age of onset with each successive generation. For example, when the CAG repeat is inherited from the father, DRPLA can manifest itself 28 years earlier than the father began having symptoms, while if transmitted from the mother, DRPLA can present 15 years earlier than the previous generation.
Author Info: Catherine L. Tesla MS, CGC, Thomson Gale, Gale, Detroit, Gale Encyclopedia of Genetic Disorders Part II, 2005This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.
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