Various aspects of mitochondrial function could be affected in PD and while studies actively seek to develop and validate the right biomarker assays for assessing PINK1-Parkin pathway in iPD, the field is also leveraging existing mitochondrial biomarker assays that are capable of detecting altered mitochondrial function, beyond mitophagy, in PINK1 and PRKN mutation carriers and iPD cases. Here, PRKN is linked to Parkinson disease.