GRN and frontotemporal dementia: However, contrary to the view that PGRN deficiency causes neurotoxicity through sphingolipid accumulation, recent lipidomic and proteomic analyses of GRN-FTD brain tissue revealed a striking loss of myelin-enriched sphingolipids (sulfatide, galactosylceramide, sphingomyelin) in frontal white matter [96].