A variant in GRN of Spanish origin presenting with heterogeneous phenotypes

The variant c.1414-1G>T in the GRN gene has previously been reported as probably pathogenic in subjects of Hispanic origin in the American continent.

We report 5 families of Spanish origin carrying this variant, including the clinical, neuroimaging, and laboratory findings.

Phenotypes were strikingly different, including cases presenting with behavioral variant frontotemporal dementia, semantic variant primary progressive aphasia, rapidly progressive motor neuron disease (pathologically documented), and tremor-dominant parkinsonism. Retinal degeneration has been found in homozygous carriers only. Ex vivo splicing assays confirmed that the mutation c.1414-1G>T affects the splicing of the exon, causing a loss of 20 amino acids in exon 11.

We conclude that variant c.1414-1G>T of the GRN gene is pathogenic, can lead to a variety of clinical presentations and to gene dosage effect, and probably has a Spanish founder effect.