[Molecular diagnosis of Prader-Willi and Angelman syndromes: methylation, cytogenetics and FISH analysis].
BACKGROUND
The diagnosis of Prader-Willi and Angelman syndromes is difficult, since their phenotypic manifestations are variable and unspecific. The study of the methylation state of DNA in 15(q11-q13) using polymerase chain reaction, called methylation test, allows the diagnosis of most patients with Prader-Willi and Angelman syndromes, irrespective if the underlying molecular alteration is a deletion, uniparental disomy or a punctual imprinting mutation.


OBJECTIVE
To assess the effectiveness of methylation test in the diagnosis of Prader-Willi and Angelman syndromes.


METHODS
Thirty seven cases with a presumptive diagnosis of Prader-Willi syndrome and 25 with the presumptive diagnosis of Angelman syndrome were studied. Methylation test was done in genomic DNA obtained from peripheral lymphocytes.


RESULTS
Methylation test confirmed the clinical diagnosis in 11 of 37 patients with Prader Willi (30%) and 6 of 25 patients with Angelman syndrome (24%).


CONCLUSIONS
Clinical criteria overestimate the diagnosis of Prader-Willi and Angelman syndromes. The initial diagnosis should be confirmed with the methylation test and, if necessary, with FISH that will detect most deletions in the region.
Santa María
L
L
Bioquímico Universidad de Chile.
Curotto
B
B
Cortés
F
F
Rojas
C
C
Alliende
M A
MA
D000293:Adolescent; D000328:Adult; D017204:Angelman Syndrome / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D019175:DNA Methylation; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D007621:Karyotyping; D008297:Male; D009154:Mutation; D016133:Polymerase Chain Reaction; D011218:Prader-Willi Syndrome / Q000175:diagnosis / Q000235:genetics*