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CAG mutation effect on rate of progression in Huntington's disease
F Squitieri1, M Cannella, M Simonelli
1Neurogenetics Unit, IRCCS Neuromed, Pozzilli (IS), Italy.
Insights
The CAG repeat expansion in Huntington's disease (HD) primarily impacts progression in rare, early-onset cases with over 90 repeats. For most patients, the CAG repeat length does not significantly influence disease severity or progression rate.
Area of Science:
- Neuroscience
- Genetics
- Neurology
Background:
- Huntington's disease (HD) is a progressive neurodegenerative disorder.
- It is characterized by a CAG trinucleotide repeat expansion in the HTT gene.
- The relationship between CAG repeat length and disease progression is not fully understood.
Purpose of the Study:
- To investigate the influence of CAG repeat length on the rate of disease progression in Huntington's disease patients.
- To determine if CAG repeat number correlates with clinical severity and onset age.
Main Methods:
- Clinical follow-up and genetic characterization of 80 Huntington's disease patients.
- Analysis of CAG repeat lengths and correlation with disease progression rates.
- Comparison of patients with infantile/aggressive forms versus typical presentations.
Main Results:
- Two patients with infantile HD (onset <10 years) had over 90 CAG repeats.
- No significant correlation was observed between CAG repeat length and disease progression in the majority of the cohort.
- CAG repeat length appears to influence disease progression only in rare, extreme cases with very early onset.
Conclusions:
- The CAG expanded repeat length significantly affects Huntington's disease progression primarily in rare cases with very high repeat numbers and early onset.
- Other genetic or environmental factors likely play a more substantial role in modulating disease severity and progression in most HD patients.
- Further research is needed to identify additional factors influencing motor symptom progression in Huntington's disease.
Abstract:
Huntington's disease (HD) is progressively invalidating and caused by a CAG expanded mutation. We tested the effect of the mutation length on the rate of progression in a cohort of 80 patients clinically followed-up and genetically characterized. Two patients presenting an infantile and aggressive HD form starting under 10 years had over 90 repeats; the other patients did not show any influence of the CAG expanded number on the rate of progression. In conclusion, the CAG expanded repeat affects the disease progression only at a very upper pathological range and in rare cases initiating very early in the life, while it does not seem to affect in any way the severity of the phenotype in most HD patients. Other factors affecting the motor symptom progression, other than the expanded repeats, therefore have to be investigated.