Department of Pediatrics/Section on Medical Genetics, Bowman Gray School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
Prader-Willi syndrome (PWS) is characterized by psychomotor
and growth retardation, infantile hypotonia, characteristic
facies, small hands and feet, dental abnormalities, and early
onset of childhood hyperphagia with consequent obesity. PWS
is associated with abnormalities of chromosome 15. Approximately
75% of patients have a deletion of 15q11q13 on the paternal
homologue, whereas 20-25% have inherited both chromosome 15s
from the mother and none from the father, a condition known
as maternal uniparental disomy (UPD). Thus, it is a lack of
paternal alleles in the 15q11q13 region that results in PWS.
Thick, sticky saliva is a consistent finding in patients with
PWS. We have characterized salivary flow and composition in
individuals with PWS. Salivary flow in patients with PWS is
approximately 20% of that in controls. In addition, the salivary
ions and proteins are present in increased amounts, possibly
reflecting a concentration effect relative to decreased water
in the saliva. Both deletion and uniparental disomy patients
exhibit these findings, suggesting that the gene(s) involved
are subject to imprinting.
