NEFL and Schnyder corneal dystrophy: To this end, we examined the relationship between HTT genotype and two biomarkers of neurodegeneration—plasma neurofilament light chain (NfL) [18] levels and brain metabolism, as assessed by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET)—in patients with SCD and MCI, characterized according to AD biomarkers.