Atypical course of Parkinson’s disease with clinical manifestations of Huntington’s disease in a patient with an allele of 27 CAG repeats in the HTT gene

• Main Authors: M. A. Nikitina, E. Yu. Bragina, M. S. Nazarenko, N. G. Zhukova, D. E. Gomboeva, K. F. Nurzhanova, N. V. Tsentr, V. M. Alifirova
• Format: Article
• Language: English
• Published: Siberian State Medical University (Tomsk) 2021-01-01
• Series: Bûlleten' Sibirskoj Mediciny
• Subjects: parkinsonism; parkinson’s disease; motor disorders; huntington’s disease; differential diagnosis; expansion of cag-repeats; htt; neurodegenerative diseases; genetics
• Online Access: https://bulletin.tomsk.ru/jour/article/view/4173
• ISSN: 1682-0363; 1819-3684

Huntington’s disease (HD) is an autosomal dominant progressive neurodegenerative disease. Its molecular cause is a cytosine-adenine-guanine (CAG) trinucleotide repeat dynamic expansion in the huntingtin (HTT) gene. Alleles with 36–39 CAG-repeats are incompletely penetrant, as individuals might develop symptoms but typically with a later age of onset. When repeats are equal or greater than 40, the symptoms of the disease occur. It is considered that CAG-repeats in the “intermediate” alleles (27–35 repeats) also cause the symptoms of the HD.We present here the case of a patient who has clinical phenotype and family history of Parkinson’s disease (PD), but 27 CAG-repeats. The feature of this patient is early development of non-motor manifestations such as cognitive impairment, psychotic disorders, early dystonia in a hand, camptocormia and poor response to levodopa. It is believed that the intermediate allele of HTT gene might modify the clinical phenotype of PD in this patient.