NEFL and autoimmune polyendocrinopathy: While other atypical Parkinson’s syndromes (APS), such as PSP, multisystemic atrophy (MSA), and corticobasal ganglion syndrome (CBS), are characterized by a marked increase in NfL level of CSF due to myelin axonal involvement, this pathological process is not typical in the early stages of PD (von Widekind et al., 2020).