CDKN1C and Pelizeaus-Merzbacher spectrum disorder: For example, BWS, which is caused by the disruption of CDKN1C or IGF2 imprinting, has been found to occur in approximately 20% of PMD cases [6]; mosaicism of maternal deletion of 11p15.5 has been found in placentas with PMD [12]; and partial trisomy of 11p15.5 (two paternal copies and one maternal copy) has been found in an enlarged placenta with edematous villi [13].