Incidence of Huntington disease in a northeastern Spanish region: a 13-year retrospective study at tertiary care centre
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RESEARCH ARTICLE
Open Access
Incidence of Huntington disease in a northeastern Spanish region: a 13-year retrospective study at tertiary care centre Paula Sienes Bailo, Raquel Lahoz* , Juan Pelegrín Sánchez Marín and Silvia Izquierdo Álvarez
Abstract Background: Despite the progress in the knowledge of Huntington disease (HD) in recent years, the epidemiology continues uncertain, so the study of incidence becomes relevant. This is important since various factors (type of population, diagnostic criteria, disease-modifying factors, etc.) make these data highly variable. Therefore, the genetic diagnosis of these patients is important, since it unequivocally allows the detection of new cases. Methods: Descriptive retrospective study with 179 individuals. Incidence of HD was calculated from the ratio of number of symptomatic cases newly diagnosed per 100,000 inhabitants per year during the period 2007–2019 in Aragon (Spain). Results: 50 (27.9%) incident cases of HD (CAG repeat length ≥ 36) were identified from a total of 179 persons studied. The remaining 129/179 (72.1%) were HD negative (CAG repeat length < 36). 29 (58.0%) females and 21 (42.0%) males were confirmed as HD cases. The overall incidence was 0.648 per 100,000 patient-years. 11/50 positive HD cases (22.0%) were identified by performing a predictive test, without clinical symptoms. The minimum number of CAG repeats found was 9 and the most common CAG length among HD negative individuals was 16. Conclusions: Our incidence lied within the range reported for other Caucasian populations. Implementation of new techniques has allowed to determine the exact number of CAG repeats, which is especially important in patients with triplet expansions in an HD intermediate and/or incomplete penetrance allele, both in diagnostic, predictive and prenatal tests. Keywords: Huntington disease, HTT gene, Incomplete penetrance alleles, Intermediate alleles
Background Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by the anomalous expansion of polyglutamine repeats (encoded by the trinucleotide CAG, Cytosine-Adenine-Guanine) in the first exon of the huntingtin gene (HTT, also known as HD or IT15 gene), located in the short arm of chromosome 4 (4p16.3) (MIM#143100) [1]. * Correspondence: [email protected] Departamento de Genética. Servicio de Bioquímica Clínica, Hospital Universitario Miguel Servet. C/ Padre Arrupe, s/n. Consultas Externas. Planta 3ª. 50009, Zaragoza, Spain
HD is an autosomal dominant disease, so the risk that each child of an affected individual inherits the mutation is 50%. On the other hand, earlier age of onset in the offspring will depend on the size of the CAGn fragment that it inherits, which tends to increase due to the phenomenon of clinical anticipation [2]. There is an inverse relationship between the number of CAG repeats and the age of onset of symptoms [3, 4]. In addition, the number of CAG repeats is also related to the age of death [5] and the rate of disease progression [6]. The repeated CAG trinucleotide i
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