These patterns also include newly discovered variants in thePSEN1 and APP genes for AD, which play critical roles inthe disease’s pathogenesis and the recurrence of a SOD1 variantpresenting as FTD without motor symptoms, suggesting a novel disease phenotype association.Families with as-yet unidentified variation remain strong candidates for future novel genediscovery as additional family members are recruited for gene-mapping linkage studies. This evidence concerns the gene APP and frontotemporal dementia.