With the advent of systems biological concepts there has been a surge of interest in biological factors, or biomarkers that can be measured and which allow the identification of individuals at risk. Biomarkers for Parkinson's disease have been identified which provide evidence of systemic metabolic dysregulation in this disorder. Such biomarkers can be studied in blood, serum and plasma but also in CSF and urine, and the study by Hoepken et al. in this issue has even made use of skin fibroblasts. The authors report on the induction of alpha-synuclein expression and suggest that the expression changes described might potentially allow objective PD patient diagnosis in an accessible, peripheral tissue. This mini-review aims to provide a broader perspective on PD functional genomics and seeks to illustrate in a systems biological context why the findings by Hoepken and colleagues are of clinical significance.