Drpla is the short form of dentatorubral pallidoluysian atrophy which is a hereditary progressive brain condition that results to involuntary movement, emotional problems and mental problems. It is believed to be brought about by the abnormal expansion of the CAG repeat that is found on the DRPLA gene. This abnormal expansion is triggered by the development of the novel neuropathology in DRPLA which implies that polyglutamine related pathogenesis involves a great par t of the central nervous system regions which are far from the previously affected systems. Drpla usually has an aspect of the neuronal disorder, lesions whose distribution depends on the CGA repeat size in the causative gene and some other multiple degeneration's.
Drpla is an autosomal dominant neurodegenerative disorder that is also referred to as the CAG repeat disease. Drpla was first reported in 1946 and it was present in two patients who were from the same family. One of the patients had a degeneration of both the pallidoluysian and the dentatorubral systems while the other had a progressive hemibalism with choreoathetosis cerebral ataxia and dementia. In 1958, another case of drpla was reported but there was no family history of the same and there was cerebral ataxia which was accompanied by degeneration of the dentato rubral and pallido luysian systems. In 1972, two cases of progressive myoclonus epilepsy with autosomal dominant transmission were reported. In 1976, eight autopsy results for eight different patients who suffered from the progressive myoclonus epilepsy confirmed its combined degeneration of the pallidoluysian and the dentratorubral systems.
Cause of drpla
Drpla is caused by the mutation of ATN1 gene that is responsible for the provision of instructions for the processing of the atrophin 1 which important for the nerve cells that are found in the brain. The ATN1 mutation involves the CAG trinucleotide repeat which comprises of three DNA building blocks known as the adenine, guanine and cytosine. In normal cases, the CAG is repeated at least 6 to 35 times within the ATN1 gene. But in people who are suffering from the drpla, the CAG segment is repeat at least 48 times with the repeat region being two to three times its normal length. This abnormally long CAG repeat tends to change the structure of atrophin1 which in turn accumulates in the neurons hence interfering with the cell functioning. This leads to the death of neurons and thus, drpla occurs.
Drpla is inherited in the autosomal pattern whereby, one copy of an altered gene is enough to cause the drpla disorder. The passing on of the drpla causes an increase in the size of the CAG repeat hence earlier onset of the drpla disorder.
Features of drpla
The drpla patients tend to show symptoms like;
- mental retardation
- lesions in the cerebral
- thickening of the skull
- small spinal cord
- slight or negligible cerebral cortical atrophy
- mild to moderate dilation of lateral ventricle
- combined degeneration of the pallidoluysian and the dentatorubral systems
- loss of neurons and the astrocytosis
- swelling and shrinking of the neurons
- poor head control
- involuntary movement
- involuntary muscle spasms