Quiz Form

Question Date: 01/10/2023

Question: 46 year old male developed insidious onset progressive chorea, dystonia, and psychosis. His wife filed for divorce. He would abuse his wife, and had hypersexuality. He was a very sober man previously. He gradually started having cognitive dysfunction-executive dysfunction, inattention, lost his job and had to be shifted to a rehab center. There was similar history in father who died at the age of 50 years <br><br>His MRI brain showed mild cerebral atrophy<br>CAG repeats in HTT gene were normal<br> Which is the genetic test most likely to be abnormal in his case?

Options:

• Senetaxin
• C9orf72
• MINGE
• SCA3

Correct Answer: C9orf72

Explaination: About 1% of patients with clinical phenotype of HD do not have CAG expansion in HTT they are described as HD phenocopies. HD phenocopy is defined asA movement disorder consistent with HD when assessed by an experienced neurologist. A negative test for the pathogenic CAG repeat expansion in HTT.A family history suggestive of autosomal dominant inheritance, cognitive impairment, behavioral, or psychiatric symptoms.Genes associated with HD phenocopy are C9orf72, SCA17, JPH3, TBP, ATN1, PRNP, VSP13A, CACNA1A, and VCP

Reference: Dupr, N. & Rouleau, G. The Puzzle of Huntington Disease Phenocopies. JAMA Neurol 73, 1056 (2016).