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As a diagnostic test for DRPLA.
Predictive testing for individuals with a family history of DRPLA. However,
a mutation should be documented first in an affected family member.
Dentatorubral-Pallidoluysian Atrophy (DRPLA) is a rare autosomal
dominant neurodegenerative disorder characterized by ataxia,
choreoathetosis, dementia and psychiatric disturbance in adults and
ataxia, myoclonus, seizures, and progressive intellectual deterioration in
children. Characteristic neuropathologic observations include
degeneration of the dentatorubral and the pallidoluysian systems of the
central nervous system.
The prevalence of DRPLA depends on the geographic and ethnic
origin of the population being studied. DRPLA was first described in a
European individual without a family history, however it is predominantly
found as an inherited condition and is particularly prevalent in Japan
(0.2-0.7 per 100,000). Although rare, DRPLA has been identified in other
populations including Europe and North America.
The underlying mutation in the ATN1 (DRPLA) gene results from
expansion of a trinucleotide (CAG) repeat. In affected individuals the
CAG repeats range from 48 to 93. As with other trinucleotide repeat
disorders, anticipation is frequently observed, and larger CAG
expansions are associated with earlier onset and a more severe and
rapid clinical course. In DRPLA, the observed anticipation appears to
be significantly greater in paternal transmissions.
Normal alleles: 7-35 CAG repeats
Abnormal alleles: 49-93 CAG repeats
An interpretive report will be provided.
A written interpretive report is provided. Interpretations take into
account the observed repeat sizes and the reason for referral.
The absence of a repeat expansion at the DRPLA locus does
not eliminate the diagnosis of other inherited neurodegenerative
disorders that have overlapping clinical features with DRPLA, such
as Huntington disease or spinocerebellar ataxias.
For predictive testing, it is important to first document the presence
of a CAG-repeat amplification in the DRPLA gene in an affected
family member to confirm that molecular expansion is the underlying
mechanism of disease transmission in the family.
In general, predictive testing is not recommended for children or
adolescents.
Medical genetic consultation is recommended, particularly for
predictive testing or when the diagnosis is atypical or uncertain.
The complex issues that surround presymptomatic diagnosis of an
untreatable disorder must be addressed.
1. Ikeuchi T, Onodera O, Oyake M, et al: Dentatorubral-
pallidoluysian atrophy (DRPLA): close correlation of CAG
repeat expansions with the wide spectrum of clinical presentations
and prominent anticipation. Semin Cell Biol 1995;6:37-44
2. Tsuji S: Dentatorubral-pallidoluysian atrophy: clinical aspects and
molecular genetics. Advances in Neurology 2002. 89:231-9,
3. Oyanagi S: Hereditary dentatorubral-pallidoluysian atrophy.
Neuropathology 2000. 20 Suppl:S42-6