NfL continued to differentiate between neurodegenerative and PPD cases when adjusted for age at assessment and sex, factors which can influence protein blood biomarker levels (Eratne et al., 2024a; Sarto et al., 2024; Simrén et al., 2022; Tsiknia et al., 2022). The gene discussed is NEFL; the disease is progressive pseudorheumatoid arthropathy of childhood.