SNCA and Parkinson disease: Finally, we must consider that in the PD patient, physiological levels of pathogenic alpha-synuclein protein become symptomatic with catastrophic downstream consequences only later in life, with the onset age of the p.A30P SNCA mutation carriers ranging from 54 to 76 years old, which is closer to sporadic PD than the p.A53T SNCA or SNCA triplication locus carriers31.