Hi guys with the NEET PG exam around the corner lets do a quick revision of a neurology topic that is asked both from genetics perspective and to test your clinical knowledge as well.

Huntington Chorea

Mnemonic: ABCD- autosomal dominant, Anticipation, Bradykinesia, Chorea, Dystonia and dementia

• Autosomal dominant condition due to defect on chromosome 4
• HTT/ Huntingtin gene: increased number of trinucleotide repeats (> 40 repeats of Poly-gutamine CAG)
• Shows Anticipation where in successive generations the disease will become more aggressive and have an earlier age of presentation.
• Defective gene leads to production of defective/mutated huntingtin protein/ inclusion bodies in neuronal cytoplasm that disrupts mitochondrial function

Neurotransmitters defect: Dopamine excess and GABA is deficient

Clinical features:

Presents between age of 25-45 years and death occurs by 60 years of age

1. Patient develops Rapid, semi purposive, Choreiform / dance like movements that are initially focal but later involve multiple body parts. Hence doing tasks like typing on keyboard of laptop or fiddling with smart phone will be difficult. A person will have hardship while doing his regular job.
2. Subsequently chorea decreases and patient develops Dystonia, rigidity and Bradykinesia. The MCQ will deliberately focus on Parkinson like features to induce errors
3. Myoclonic jerks
4. Difficulty in speaking: Dysarthria which will cause poor performance in office while making an presentation
5. Difficulty in initiating eye movements while tracking an object. Person will be highly distracted during visual fixation
6. Behavioral disturbances and cognitive impairment. Subcortical Dementia is seen
7. Significant weight loss in spite of adequate calorie intake
8. Depression with suicidal tendency / Psychosis
9. Increased incidence of type 2 Diabetes mellitus and Hypothalamic Hamartoma
10. In about 10% cases younger patients will develop akinetic rigid Parkinson syndrome called Westphal variant

Work up

1. 1. MRI head: atrophy of caudate nucleus and putamen. The distance between heads to caudate nucleus on both sides increases. Later cortical atrophy can be seen and box car appearance of ventricles
      
   2. PCR for Huntington gene

Treatment

1. 1. Synaptic Dopamine deplete: Tetrabenazine
   2. Psychosis: Clozapine (Side effect: Agranulocytosis)
   3. Sigma 1 receptor: Pridopidine
   4. Supplements of Resveratrol