Interestingly, we confirmed that CHIT1 levels are reduced in FTD and controls that are heterozygous or homozygous for the CHIT1 24-bp duplication [23] but also found that the CSF levels did not differ between wild-types and CHIT1 24-bp duplication heterozygotes in AD and prion disease. The gene discussed is CHIT1; the disease is Alzheimer disease.