Phenotypic Variability associated with the C9ORF72 Hexanucleotide Repeat Expansion: A Sporadic Case of Frontotemporal Lobar Degeneration with Prodromal Hyposmia and Predominant Semantic Deficits

Abstract

We describe a sporadic case of frontotemporal lobar degeneration, associated with the C9ORF72 mutation, with prominent behavioral changes and semantic deficits. Predominant deficits in naming, vocabulary, word comprehension, and face and object recognition emerged on neuropsychological assessment. Amnesia, behavioral changes, and isolated psychotic symptoms were also present. Hyposmia was an unspecific prodromal sign. Brain imaging showed basofrontal and temporopolar hypometabolism bilaterally, and predominantly left-sided atrophy. Levels of cerebrospinal fluid biomarkers (amyloid-β, tau and p-tau) were normal. This description further confirms the heterogeneous presentation of the C9ORF72 mutation.