A case of juvenile huntington disease in a 6-year-old boy

Abstract

Huntington disease is a neurodegenerative disorder distinguished by the triad of dominant inheritance, choreoathetosis and dementia, usually with onset in the fourth and fifth decades. It is caused by an unstable cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in the gene IT15 in locus 4p16.3. Juvenile HD that constitutes about 3% to 10% of all patients is clinically different from adult-onset form and characterized by a larger number of CAG repeats typically exceeding 60. We report a case of a 6-year-old boy with myoclonic seizure and 140 CAG repeats confirmed by molecular genetic analysis.

Keywords: Juvenile Huntington disease; Seizure; Trinucleotide repeat expansions.

Figure 1

Pedigree of the patient. I-2 had a history of involuntary movement and deceased at 50 years of age. II-1 had similar kind of abnormal movement and had been bed-ridden state since a few years ago. But genetic test of HD was not performed for both of them. II-4, the patient’s father, was diagnosed of HD at 32 years. II-6 and III-1(the patient) was diagnosed at the age of 30 years and 6 months respectively by presymptomatic test. HD: Huntington disease.

Figure 2

MRI of the patient. Brain MRI showed atrophic change of putamen, caudate nucleus, cerebral cortex and cerebellum. Flattening of wall of frontal horn with ventriculomegaly is remarkable. There is no abnormally enhancing lesion. MRI: magnetic resonance image.