Serum I-FABP concentration was higher in males (median [5, 95 percentiles] 451 [221, 1088] pg/ml) than in females (392 [195, 846] pg/ml) (Wilcoxon rank-sum test, P = 0.03), the gender effect being confined to PD (P = 0.01). This evidence concerns the gene FABP2 and Parkinson disease.