Clinical manifestations of homozygote allele carriers in Huntington disease
Por:
Cubo, E, Martinez-Horta, SI, Santalo, FS, Descalls, AM, Calvo, S, Gil-Polo, C, Munoz, I, Llano, K, Mariscal, N, Diaz, D, Gutierrez, A, Aguado, L, Ramos-Arroyo, MA
Publicada:
30 abr 2019
Resumen:
Objective
Because patients homozygous for Huntington disease (HD) receive the gain-of-function mutation in a double dose, one would expect a more toxic effect in homozygotes than in heterozygotes. Our aim was to investigate the phenotypic differences between homozygotes with both alleles >= 36 CAG repeats and heterozygotes with 1 allele >= 36 CAG repeats.
Methods
This was an international, longitudinal, case-control study (European Huntington's Disease Network Registry database). Baseline and longitudinal total functional capacity, motor, cognitive, and behavioral scores of the Unified Huntington's Disease Rating Scale (UHDRS) were compared between homozygotes and heterozygotes. Four-year follow-up data were analyzed using longitudinal mixed-effects models. To estimate the association of age at onset with the length of the shorter and larger allele in homozygotes and heterozygotes, regression analysis was applied.
Results
Of 10,921 participants with HD (5,777 female [52.9%] and 5,138 male [47.0%]) with a mean age of 55.1 +/- 14.1 years, 28 homozygotes (0.3%) and 10,893 (99.7%) heterozygotes were identified. After correcting for multiple comparisons, homozygotes and heterozygotes had similar age at onset and UHDRS scores and disease progression. In the multivariate linear regression analysis, the longer allele was the most contributing factor to decreased age at HD onset in the homozygotes (p < 0.0001) and heterozygotes (p < 0.0001).
Conclusions
CAG repeat expansion on both alleles of the HTT gene is infrequent. Age at onset, HD phenotype, and disease progression do not significantly differ between homozygotes and heterozygotes, indicating similar effect on the mutant protein.
Classification of evidence
This study provides Class II evidence that age at onset, the motor phenotype and rate of motor decline, and symptoms and signs progression is similar in homozygotes compared to heterozygotes.
Filiaciones:
Cubo, E:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Martinez-Horta, SI:
Hosp Santa Creu & Sant Pau, Dept Neurol, Movement Disorders Unit, Barcelona, Spain
Ctr Invest Red Enfermedades Neurodegenerat CIBERN, Madrid, Spain
Santalo, FS:
Hosp Santa Creu & Sant Pau, Dept Neurol, Movement Disorders Unit, Barcelona, Spain
Ctr Invest Red Enfermedades Neurodegenerat CIBERN, Madrid, Spain
Descalls, AM:
Fdn Jimenez Diaz, Dept Neurol, Madrid, Spain
Calvo, S:
Hosp Univ Burgos, Res Unit, Burgos, Spain
Gil-Polo, C:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Munoz, I:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Llano, K:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Mariscal, N:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Diaz, D:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Gutierrez, A:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Aguado, L:
Hosp Univ Burgos, Dept Neurol, Burgos, Spain
Ramos-Arroyo, MA:
Complejo Hosp Navarra, Dept Genet, Pamplona, Spain
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