Which human genetic disorder results from loss of paternal gene expression on chromosome 15?

Prader–Willi syndrome results from loss of paternal gene expression in a region of chromosome 15.

The condition is an example of genomic imprinting, in which the activity of some genes depends on whether the copy was inherited from the mother or the father. In Prader–Willi syndrome, paternally expressed genes in chromosome region 15q11-q13 are absent or inactive.

Common mechanisms include deletion of the paternal region, maternal uniparental disomy, or an imprinting defect. Clinical features can include low muscle tone and feeding problems in infancy, followed later by marked appetite dysregulation and intellectual or developmental difficulties.

Angelman syndrome involves the same broad chromosome region but usually reflects loss of maternal UBE3A expression in the brain. That parent-of-origin distinction is the key difference between the two syndromes.