Genetics exert an important role in disease susceptibility and alterations in chromosome 9 open reading frame 72 (C9orf72), superoxide dismutase 1 (SOD1), TAR DNA binding protein-43 (TARDBP), and fused in sarcoma (FUS), the most common ALS-related genes, show a high selectivity for motor neuron degeneration, although they have also been associated to other disorders, such as frontotemporal dementia and PD [291]. Here, SOD1 is linked to Parkinson disease.