USMLE Step 1 Neuroanatomy Review 25 23 Huntington’s Disease, Sydenham’s Chorea

USMLE Step 1 Neuroanatomy Review 25 23 Huntington’s Disease, Sydenham’s Chorea

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Play USMLE Audio MP3 25 23 Huntington’s Disease, Sydenham’s Chorea Below

Begin 25 23 Huntington’s Disease, Sydenham’s Chorea Transcription

What is the genetic disorder affecting the caudate nucleus and the putamen, which is characterized by the gradual onset and subsequent progression of chorea and dementia. This is Huntington’s disease.

Where is the gene defect in Huntington’s disease?

  • It is a single defect in the short arm of chromosome 4.

And what is the inheritance of Huntington’s disease?

  • Autosomal dominant.

What chance does an offspring of an affected patient have on developing Huntington’s?

  • 50%.

Are the symptoms the same in the homozygous as in the heterozygous cases?

  • Yes, there is no difference in the symptoms between homozygous and heterozygous in Huntington’s.

When do symptoms usually appear in huntington’s disease?

  • Usually in adulthood between the ages of 30-50 years of age.

What degenerates in the caudate nucleus and putamen in Huntington’s disease?

  • Both the cholinergic and the GABAergic neurons degenerate in Huntington’s disease.

Now what are the neurons particularly spared in Huntington’s disease?

  • The neurons which contain NADPH diaphorase.

Now what disorder affecting the striatum occurs frequently in children and adolescents as a complication of a previous infection?

  • This is Sydenham’s chorea.

And what sort of infection is Sydenham’s chorea associated with?

  • A previous group A streptococcal infection.

What is the pathological process by which this previous group A streptococcal infection results in Sydenham’s chorea?

  • A necrotizing arteritis in the thalamus, caudate nucleus, and putamen.


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