Question 10
(Source: Professor Yasser Metwally, 2008)
51 year old woman is brought by neighbors with symptoms of abnormal movements since several days now. The woman stays alone and there are distant relatives who come to visit often. The woman's past medical file on record do not say about anything significant but there is a history about her father having some movement disorder at the age of 55 and that he died of aspiration pneumonia. The examination findings are given above in the video. The doctor suspects some neurological inherited disorder. Where is the neurological defect located in this patient?
A) Globus Pallidus, due to GAA repeat on short arm of chromosome 9
B) Caudate nucleus, due to GAA repeat on short arm of chromosome 9
C) Caudate nucleus, due to CAG repeat on short arm of chromosome 4
D) Caudate nucleus, due to CAG repeat on long arm of chromosome 4
D) Substantia nigral pathway
E) Mitral Valve vegetations
F) Caudate nucleus, due to CTG repeat on long arm of chromosome 19
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Answer: C) Caudate nucleus, due to CAG repeat on short arm of chromosome 4.
The patient in the vignette is most likely suffering from Huntington's disease. The media shows sudden jerky purposeless movements called Chorea which is characteristic of basal ganglia lesion (especially the caudate). Huntington's disease is an autosomal dominant disease with trinucleotide repeat disorder on the short arm of chromosome 4. Its is characterised by chorea, rigidity, and dementia.
Hint in the question: Father having the disorder and dies of aspiration pneumonia (MCC of death in these patients).
There is no cure for the disease. Palliative treatment with tetrabenazine and neuroleptics are tried with some success.
Points to note:
1) Trinucleotide repeat disorders:
* Amplification of sequence of nucleotides.
* Increase severity in subsequent generation (Anticipation)
* Eg: Fragile X Syndrome, huntington's disease, Friedrich's Ataxia, & Myotonic dystrophy.
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