Session Time: 12:00pm-1:30pm
Location: Exhibit Hall located in Hall B, Level 2
Objective: To describe clinical manifestations in carriers of intermediate alleles (IAs) of CAG trinucleotides in HTT gene of Mexican population.
Background: Huntington’s disease (HD) is a neurodegenerative disorder characterized by behavioral, motor and cognitive impairments. Is caused by a trinucleotide CAG expansion in exon 1 of the HTT gene at chromosome 4p. The most common CAG size in the general population is 17 repeats, the presence of 40 or more CAG repeats confers the classical Huntington disease phenotype, meanwhile 36 to 39 repeats are considered alleles with reduced penetrance with late onset disease. On the other hand, alleles with 27-35 repeats are known as IAs. Previously, it was believed that IAs do not confer disease, however the description of isolated cases with HD phenotype and more recently the two prospectives studies (PHAROS and COHORT) have associated the presence of IAs with more significant behavioral issues but normal motor and cognition abilities.
Methods: After approval by local ethics committee and informed consent, all those subjects who had been previously evaluated to HD molecular test that were resulted with IAs, were included in a group (cases) and were matched with 2 healthy individuals by age and sex (controls). Each group were applied motor scale from Unified HD Rating Scale (UHDRS) and the instrument Problem Behaviors Assessment for HD (PBA-HD). To evaluate differences in the groups Mann-Whitney U test was performed.
Results: The cases group (5 individuals) showed significant differences in most of the items evaluated by motor scale from UHDRS in comparison with controls (
|UHDRS Motor Assessment||Cases Median (minimum and maximum)||Controls Median (minimum and maximum)||p value|
|Tongue protrusion||0 (0-3)||0||.254|
|Luria||3 (2-4)||0 (0-1)||.001*|
|Rigidity – Arms|
|Tandem walking||2 (1-3)||0||.001*|
|Retropulsion pull test||1 (0-3)||0||.013*|
|Diagnosis confidence level||2 (1-3)||0||.001*|
|Motor examination||45 (19-83)||0.5 (0-3)||.001*|
|PBS-HD||Cases Median (minimum and maximum)||Controls Median (minimum and maximum)||p value|
|Poor judgment, self-monitoring|
|Frecuency||3 (1-5)||1 (1-2)||.028*|
|Frecuency||3 (2-5)||1 (1-2)||.008*|
|Severity||2 (1-3)||0 (0-2)||.005*|
|Sleeping or drowsy during day|
|Frecuency||3 (2-5)||2 (1-3)||.019*|
|Frecuency||3 (3-5)||2 (1-2)||.001*|
|Loss of volition|
|Frecuency||3 (1-5)||1 (1-1)||.013*|
|Severity||1 (0-3)||0 (0-0)||.013*|
|Frecuency||4 (1-4)||1 (1-3)||.028*|
|Severity||3 (1-5)||1.5 (1-2)||.040*|
Conclusions: The clinical description of our IAs carriers allows us to partake in the deciphering of a newly discovered field in medicine. This contributes widely to know the potential phenotypic spectrum of HD, allowing early assessment and possible treatment to the manifestations present in these individuals. Our research seeks to describe clinical manifestations in carriers of IA, justified in assuming that such alleles are associated with subtle data or mild cases of HD. We can show that motor impairment is bigger than psychiatric disorders in our sample of Mexican individuals with IA.
To cite this abstract in AMA style:M.A. Ramírez-García, D.J. Dávila-Ortiz de Montellano, P. Yescas-Gómez, A. Ochoa-Morales, C. Boll, M.E. Alonso-Vilatela. Clinical and behavioral features in carriers of intermediate length alleles of HTT gene. A case series of Mexican population [abstract]. Mov Disord. 2016; 31 (suppl 2). https://www.mdsabstracts.org/abstract/clinical-and-behavioral-features-in-carriers-of-intermediate-length-alleles-of-htt-gene-a-case-series-of-mexican-population/. Accessed September 21, 2023.
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