Two major observations of the current study are: (1) the expression of CHCHD2 was reduced significantly in human erythrocytes, substantia nigra of brain collected at autopsy, and mice carrying transgenic mutant A53T α-synuclein; and (2) the expression of CHCHD2 in erythrocytes, a readily accessible clinical sample source, could be an early diagnostic marker of PD. Here, CHCHD2 is linked to Parkinson disease.