Department of Pathology, University of Oklahoma Health Sciences Center

NeuroTest Question #7 Next question Previous question

Answer: D (Due to abnormal expansion of CAG-trinucleotide repeats)

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Discussion: 

• Pathology: The caudate (ß) is missing in this coronal section and is consistent with Huntington disease. 
• Molecular pathology and genetics: Huntington disease is transmitted in an autosomal dominant pattern with genetic anticipitation; sporadic cases can also occur. The gene being involved is located on chromosome 4p16.3 and code for the protein Huntingtin. Huntington disease is associated with abnormal expansion of CAG-trinucleotide repeats in the coding region of the gene. 
• CTG-repeats: Abnormal tandem CTG-repeats in non-coding regions are found in myotonic dystrophy and spinal cerebellar ataxia type VIII (SCA-8). 
• General rule: As a general rule, CAG-repeats are found in coding regions and non-CAG repeats are found in non-coding regions.

Comment: KarMing-Fung@ouhsc.edu