SNCA and autism spectrum disorder: In degenerative brain diseases like Parkinson's disease (PD), alpha-synuclein (a-syn) can be in its monomeric (a-syn-mono) or toxic oligomeric (a-syn-oligo) or as a total (a-syn-total) forms in the biological body fluids including saliva. Past research has observed major a-syn plasma variations in children with autism spectrum disorder (ASD) pointing toward brain degenerative components in their pathophysiology.