Allan-Herndon-Dudley syndrome is a rare disorder of brain development that results in intellectual disability and movement difficulties. It is a rare syndrome that occurs in the fetus and is more common in males than females. There are approximately 25 families with Allan-Herndon-Dudley syndrome reported worldwide.

For most chromosomes, uniparental disomy (UPD) occurs without any serious clinical consequences. However, for chromosomes with genetic imprints, the expression of some genes with genetic imprints from the father and mother is different in the case of UPD, which can lead to the expression of some genetic syndromes.