Analysis of Heritability Across the Clinical Phenotypes of Frontotemporal Dementia and the Frequency of the C9ORF72 in a Colombian Population.
Level 4 - case-series / case-control
Cross-sectional case series evaluating family history and genetic frequency in an observational cohort
PubMed 34526954 · doi:10.3389/fneur.2021.681595
What was done
A cohort of 132 Colombian patients diagnosed with frontotemporal dementia (FTD)—including behavioral variant FTD (bvFTD), logopenic variant primary progressive aphasia (PPA), non-fluent agrammatic PPA, and semantic variant PPA—was evaluated for hereditary risk. Risk was categorized into four levels (high, medium, low, and apparently sporadic) based on criteria by Wood et al. All participants were screened for C9ORF72 G4C2 hexanucleotide repeat expansions (>30 repeats).
What was found
bvFTD was the most common phenotype (62.12%), with no significant demographic differences across phenotypes. By hereditary risk criteria, 54.4% (72/132) were sporadic, 17.4% (23/132) were high risk, 17.4% (23/132) were low risk, and 10.6% (14/132) were medium risk. The C9ORF72 repeat expansion frequency was 0.76% (1/132).
Why it matters
Unlike Caucasian populations where C9ORF72 expansions account for up to 37.5% of familial FTD cases, the mutation is very rare in this Colombian population, highlighting the need to investigate other genetic etiologies in diverse cohorts.
Limits
The study is limited by a modest sample size (n = 132), absence of healthy control comparisons, and genetic analysis restricted solely to C9ORF72 hexanucleotide expansions without screening for other known FTD causative genes.
Cited by
- supports Approximately 30% of frontotemporal dementia cases are genetic or familial, while 70% of cases are sporadic.