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Let's talk about some other

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genetic causes of chorea.

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I'd like to start out with the

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entity known as HDL2,

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which is caused by mutations in the

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gene encoding junctophilin-3,

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which bears a striking resemblance

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to Huntington's chorea.

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You might be saying to yourself, what is that?

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How do I diagnose it?

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Well, it's pretty easy, actually.

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If you see something that resembles

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Huntington's Chorea in somebody of African or

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African-American ancestry,

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then you should be thinking about

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this disorder and check for it genetically.

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Clinical varieties of inherited prion diseases

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also include a Huntington disease-like

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phenotype called HDL1,

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where a 192 nucleotide is inserted in the region

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of PRNP encoding, an octapeptide repeat.

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In other words,

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eight peptides that repeat in the prion protein.

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Now, how would you diagnose this?

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You go right to your FLAIR

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and you'd start looking at persistent signal

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alterations in the caudoputamen region

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or in the cortices that persist,

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they don't enhance,

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they don't go away.

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They may or may not diffusion restrict,

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and the patients have a slow progressive disorder.

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Signal alterations on a FLAIR image in

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Huntington's disease don't occur till very late

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in the disease. So that would be a tip-off

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you're dealing with a prion look-alike.

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Some types of spinocerebellar ataxia types 2,

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3, and 17 can rarely present with prominent

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choreic movement disorders.

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In particular, types 3 and 17 may produce

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notable clinical similarities to HD

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or Huntington's chorea.

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The same is true for the entity,

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difficult to say,

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Dentatorubral Pallidoluysian Atrophy.

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Another CAG repeat disease

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or cytosine adenine guanine repeat

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with mutations of the gene

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encoding the atrophic-1 protein

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located on chromosome twelve.

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For those of you that are taking an examination,

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remember that Huntington's is seen

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on chromosome number four.

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Other rare causes for genetic chorea such as

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autosomal recessive cerebellar ataxias with

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oculomotor apraxia include ataxia telangiectasia,

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ataxia telangiectasia-like disorders and ataxia

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with oculomotor apraxia types 1 and 2.

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Then you get into metabolic disorders like

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Wilson's disease, which is an important one,

2:39

and potentially treatable,

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paroxysmal kinesigenic choreoathetosis,

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infantile convulsions, paroxysmal choreoathetosis,

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and the last, pantothenate kinase-associated neural

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degeneration, previously known as the

2:58

artist Hallervorden-Spatz disease,

3:01

also known as pigmentary degeneration

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of the globus pallidus.

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Remember, you really shouldn't see much

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iron accumulation in the globus pallidus

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until about age 12 or 13.

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So those are some wannabes,

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some look-alikes, genetically mediated

3:18

that simulate Huntington's chorea.