A Novel CHMP2B Splicing Variant in Atypical Presentation of Familial Frontotemporal Lobar Degeneration

C-truncating variants in the charged multivesicular body protein 2B (CHMP2B) gene are a rare cause of frontotemporal lobar degeneration (FTLD), previously identified only in Denmark, Belgium, and China. We report a novel CHMP2B splice-site variant (c.35-1G>A) associated with familial FTLD in Spain. The cases were two monozygotic male twins who presented at ages 62 and 66 years with a slowly progressive behavioral variant of frontotemporal dementia and a syndrome mimicking dementia with Lewy bodies, respectively. Functional and in silico analyses supported the pathogenicity of this variant. Our findings contribute new insights into the genetic landscape and clinical heterogeneity of FTLD.