SNCA and Parkinson disease: However, in the same group of patients, two other protein pathologies were measured: alpha-synuclein (SNCA, associated with several diseases of the Parkinson spectrum) was present in 41–55% and transactive response DNA-binding protein 43 kDa (TDP-43, associated with amyotrophic lateral sclerosis and frontotemporal dementia) in 33–40% of patients (Figure 3) (Robinson et al., 2018b).