While further studies involving greater numbers of VPS35[D620N] patients are needed to confirm that the VPS35[D620N] mutation stimulates Rab protein phosphorylation in humans, we are intrigued by the significant increase in Rab10 phosphorylation observed in peripheral blood cells from the three PD patients carrying the VPS35[D620N] mutation. Here, VPS35 is linked to Parkinson disease.