However, we cannot exclude the possibility that another pathogenic gene(s) is involved in the development of PD in addition to MIDN. For example, MIDN deletion in the British population cohort (38 of 142 of study cases, and 4 of 47 of controls) spans EFNA2, encoding ephrin A2 protein (Fig. 1). Here, EFNA2 is linked to Parkinson disease.