How many people have cri du chat syndrome?

1/20k-1/50k births. The listed frequency of cri du chat syndrome is 1/20, 000-1/50, 000 births. The partial deletion of chromosome 5 is thought to represent 85% by spontaneous new mutations and 15% from an abnormal chromosomal contribution from an unaffected parent that carries a balanced rearrangement of chromosomal material.