Diagnóstico molecular de los síndromes de Prader-Willi y de Angelman: análisis de metilación, citogenética y FISH / Methylation, citogenetic and FISH tests in the molecular diagnosis of Prader-Willi and Angelman syndromes

ABSTRACT

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 l5(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 Iymphocytes. Results: Methylation test confirmed the clinical diagnosis in 11 of 37 patients with PraderWilli (30 percent) and 6 of 25 patients with Angelman syndrome (24 percent). 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