Comparison of Phenotype Between Patients With
Prader-Willi Syndrome Due to Deletion 15q and
Uniparental Disomy 15
Prader-Willi syndrome (PWS) is a complex
multiple anomaly syndrome that has been
shown to result from deficient expression of
paternal chromosome 15(q11-q13). In most
cases, it is caused either by deletion of this
region in the paternally inherited chromosome
15 or by maternal uniparental disomy
(UPD) of chromosome 15. In order to determine
whether there are phenotypic differences
between patients whose PWS is caused
by these two different mechanisms, 54 affected
individuals (37 with deletion, 17 with
UPD) were personally examined and studied
using molecular techniques. The previously
recognized increased maternal age in patients
with UPD and increased frequency of
hypopigmentation in those with deletion
were confirmed. Although the frequency and
severity of most other manifestations of PWS
did not differ significantly between the two
groups, those with UPD were less likely to
have a “typical” facial appearance. In addition,
this group was less likely to show some
of the minor manifestations such as skin
picking, skill with jigsaw puzzles, and high
pain threshold. Females and those with UPD
were also older, on average. Possible mechanisms
by which these differences could occur
and the implications of these differences for
diagnosis are described. Am. J. Med. Genet.
68:433–440, 1997. © 1997 Wiley-Liss, Inc.
KEY WORDS: Prader-Willi syndrome; 15q
deletion; uniparental disomy;
microdeletion; FISH; methylation
analysis
Comparison of Phenotype Between Patients WithPrader-Willi Syndrome Due to Deletion 15q andUniparental Disomy 15Prader-Willi syndrome (PWS) is a complexmultiple anomaly syndrome that has beenshown to result from deficient expression ofpaternal chromosome 15(q11-q13). In mostcases, it is caused either by deletion of thisregion in the paternally inherited chromosome15 or by maternal uniparental disomy(UPD) of chromosome 15. In order to determinewhether there are phenotypic differencesbetween patients whose PWS is causedby these two different mechanisms, 54 affectedindividuals (37 with deletion, 17 withUPD) were personally examined and studiedusing molecular techniques. The previouslyrecognized increased maternal age in patientswith UPD and increased frequency ofhypopigmentation in those with deletionwere confirmed. Although the frequency andseverity of most other manifestations of PWSdid not differ significantly between the twogroups, those with UPD were less likely tohave a “typical” facial appearance. In addition,this group was less likely to show someof the minor manifestations such as skinpicking, skill with jigsaw puzzles, and highpain threshold. Females and those with UPDwere also older, on average. Possible mechanismsby which these differences could occurand the implications of these differences fordiagnosis are described. Am. J. Med. Genet.68:433–440, 1997. © 1997 Wiley-Liss, Inc.KEY WORDS: Prader-Willi syndrome; 15q
deletion; uniparental disomy;
microdeletion; FISH; methylation
analysis
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