Serotonin transporter gene polymorphic element 5-HTTLPR increases the risk of sporadic Parkinson 's disease in Italy .
B-GeneOrGeneProduct I-GeneOrGeneProduct O O O B-GeneOrGeneProduct O O O O O B-DiseaseOrPhenotypicFeature I-DiseaseOrPhenotypicFeature I-DiseaseOrPhenotypicFeature O O O