[Molecular diagnosis of Prader-Willi and Angelman syndromes: methylation, cytogenetics and FISH analysis]
L Santa María1, B Curotto, F Cortés
1Bioquímico Universidad de Chile.
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.
Aim:
To assess the effectiveness of methylation test in the diagnosis of Prader-Willi and Angelman syndromes.
Patients And 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.
