Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Paper Eur Neurol 2007;57:26–30 DOI: 10.1159/000097006 Monozygotic Twins Suffering from Huntington’s Disease Show Different Cognitive and Behavioural Symptoms J.C. Gómez-Esteban E. Lezcano J.J. Zarranz F. Velasco Iñigo Garamendi Tomás Pérez Beatriz Tijero Neurology Service, Movement Disorders Unit, Cruces Hospital, Neurosciences Department, Basque Country University, Baracaldo, Spain Introduction Huntington’s disease (HD) is a neurodegenerative dis- ease characterized by a combination of extrapyramidal symptoms (hyperkinetic, in most cases), cognitive dete- rioration and psychiatric symptoms [1, 2]. HD is caused by a pathological expansion of the CAG trinucleotide in the IT 15 (4p 16.3) gene [3]. Polyglutamine intranuclear inclusions are found in the affected neurons, especially in the striatal body [4, 5]. It is already well established that the number of tri- nucleotide repeats affects the age of onset negatively [7] and disease progression [6] positively. However, no cor- relation with the symptomatology has been observed to date. Environmental factors have an influence on the clini- cal manifestation of HD and other genetically deter- mined diseases. Therefore, studies conducted in twins are important in order to define the phenotype and, even- tually, to modify external factors influencing the clinical picture. Twin studies are scarce in HD probably due to its low prevalence. This is a case report of 2 monozygotic HD twins fol- lowed up for 30 months with scales that quantified motor situation, cognitive status, behavioural disorders and de- pressive symptoms. Key Words Huntington’s disease  Twins, homozygotic  Huntington’s disease, cognition, behaviour Abstract Monozygotic male twins, carrying the same number of tri- nucleotide repeats in the IT 15 Huntington disease (HD) gene, showed a different clinical course. Patient 1 presented with anxiety and chorea at the age of 40. Patient 2 showed persecution paranoia and motor impersistence at the age of 42. Both patients were monitored for 30 months using cur- rently recommended motor and behaviour scales. No differ- ences were observed in motor scoring besides small inter- evaluation fluctuations. However, on the cognitive and behaviour scales, patient 1 showed a significant worsening when compared with patient 2. Our cases support the belief that the motor symptoms and signs in HD are highly depen- dent on the trinucleotide expansion. However, the differenc- es in the evolution of mental status in our patients suggest that other still unknown environmental factors are impor- tant in the phenotypic expression of Huntington’s disease. Copyright © 2007 S. Karger AG, Basel Received: April 19, 2006 Accepted: August 16, 2006 Published online: November 14, 2006 Juan Carlos Gómez-Esteban Servicio de Neurología, Hospital de Cruces Plaza de cruces sn ES–48903 Baracaldo (Spain) Tel. +34 63 976 8124, Fax +34 94 600 9075, E-Mail jgomeze@meditex.es © 2007 S. Karger AG, Basel 0014–3022/07/0571–0026$23.50/0 Accessible online at: www.karger.com/ene