Table 3. [Selected Genes in the Differential Diagnosis of Adult-Onset DRPLA]. - GeneReviews®

Gene(s)	Disorder	Comment
HTT	Huntington disease (HD)	The presence of ataxia is important for differentiating DRPLA from HD. Some persons w/the non-PME phenotype of DRPLA may initially be diagnosed as having HD, as the main clinical features in these persons are involuntary movements & dementia, symptoms that often mask the presence of ataxia. The history of ataxia as an early symptom as well as atrophy of the cerebellum and brain stem (particularly pontine tegmentum) on imaging study is important in the differential diagnosis. Atrophy of the caudate nucleus favors the diagnosis of HD. It is frequently necessary to do molecular genetic testing for Huntington disease, Huntington disease-like phenotypes, and DRPLA in persons w/unexplained progressive dementia & involuntary movements.
JPH3	Huntington disease-like 2
PRNP	Genetic prion disease
~40 genes incl: ATXN1 ATXN2 ATXN3 ATXN7 ATXN8 ATXN10 CACNA1A TBP	Autosomal dominant cerebellar ataxias (See Hereditary Ataxia Overview.)	Persons w/DRPLA who have mildly expanded CAG repeats (c.1462CAG[49_55]) tend to exhibit, particularly in early stages, pure cerebellar symptoms such as ataxia w/o dementia, choreoathetosis, or character changes, making the clinical diagnosis of DRPLA difficult. Such persons need to be distinguished from those w/ataxia of other etiologies.

Gene(s)

Disorder

Comment

HTT

The presence of ataxia is important for differentiating DRPLA from HD. Some persons w/the non-PME phenotype of DRPLA may initially be diagnosed as having HD, as the main clinical features in these persons are involuntary movements & dementia, symptoms that often mask the presence of ataxia. The history of ataxia as an early symptom as well as atrophy of the cerebellum and brain stem (particularly pontine tegmentum) on imaging study is important in the differential diagnosis. Atrophy of the caudate nucleus favors the diagnosis of HD. It is frequently necessary to do molecular genetic testing for Huntington disease, Huntington disease-like phenotypes, and DRPLA in persons w/unexplained progressive dementia & involuntary movements.

JPH3

Huntington disease-like 2

PRNP

Genetic prion disease

~40 genes incl:
ATXN1
ATXN2
ATXN3
ATXN7
ATXN8
ATXN10
CACNA1A
TBP

Autosomal dominant cerebellar ataxias (See Hereditary Ataxia Overview.)

Persons w/DRPLA who have mildly expanded CAG repeats (c.1462CAG[49_55]) tend to exhibit, particularly in early stages, pure cerebellar symptoms such as ataxia w/o dementia, choreoathetosis, or character changes, making the clinical diagnosis of DRPLA difficult. Such persons need to be distinguished from those w/ataxia of other etiologies.

From: DRPLA

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Adam MP, Feldman J, Mirzaa GM, et al., editors.

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