NEFL and Friedreich ataxia: NfL plasma concentrations were higher in children with FRDA (28.5 ± 7.7 pg/mL) in comparison with both age-matched control (5.3 ± 2.7 pg/mL; P < 0.001) and adult FRDA patients (21.6 ± 8.1; P < 0.04) (Table 1; Fig. 1A).