Use of two FISH probes provides a cost-effective,simple protocol to exclude an imprinting centre defect in routine laboratory testing for suspected Prader-Willi and Angelman syndrome

From among the many suspected patients with Prader-Willi (PWS) or Angelman (AS) syndromes received for diagnosis in a routine genetics laboratory, we present our protocol for the exclusion of a possible, rare imprinting centre (IC) defect. Deletion detection utilising two FISH probes-SNRPN within the IC, and another probe outside the IC, on the same suspension remaining from the cytogenetic harvest, provides a simple, quick and cost-effective system for exclusion of an IC defect, for patients with an abnormal methylation analysis.