Two cases of CHM with expression of p57KIP2 due to retention of a maternally derived chromosome 11 have been described [12, 13], in addition to two PHM in which no expression of p57KIP2 was found in either cytotrophoblast or villous stroma due to loss of the maternal copy of chromosome 11 [3, 14]. This evidence concerns the gene CDKN1C and choroideremia.