SNCA and Parkinson disease: The mutation was identified in a large family (referred to as the “Contursi kindred”) with an autosomal-dominantly inherited form of parkinsonism in a gene (the gene is abbreviated as SNCA, the protein as αSYN), with a single base-pair change from alanine (A) to threonine (T) at position 53 of αSYN (A53T) causing the disease with high, but not complete, penetrance.