The possibility of a cumulative effect of the metabolic and/or mitochondrial perturbations resulting from the MMUT deficiency and the loss of PINK1/Parkin-mediated quality control systems is also supported by the observation that patients harbouring loss-of-function mutations of PINK1 causing Parkinson’s disease survive in the absence of functional PINK1-dependent mitophagy pathway3. Here, PRKN is linked to Parkinson disease.