Amyloid-positive cotton wool plaques may be common hallmarks among PSEN1 mutation cases with spastic paraplegia (or Parkinsonism), such as the deletion of residue 84–84, Pro436Gln, Arg278Gln and Pro284Leu or the deletion of PSEN1 exon 9. The gene discussed is PSEN1; the disease is Parkinsonism.