We examined 54 patients with deletion-negative Angelman syndrome (AS) using DNA methylation testing and microsatellite polymorphism analysis, and identified three patients with paternal uniparental disomy (UPD) and seven patients with imprinting defects (ID). The three patients with UPD were shown to have paternal isodisomy 15, which we hypothesized to have arisen from duplication of chromosome 15. Two of the patients with ID were siblings and carried microdeletions of the imprinting center (IC), while the remaining five patients had no evidence of deletions and represented sporadic cases. Two of the three patients with UPD and two of the seven patients with ID had not developed seizures. The only patients displaying microcephaly were those with ID who had microdeletions at the IC. These data support the previous findings that indicate that patients with UPD and ID may have a milder phenotype of AS.
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Accepted: December 16, 2003
Received in revised form: November 24, 2003
Received: August 19, 2003
☆The paper is based on the lecture given at the sixth annual meeting of the Infantile Seizure Society, Tokyo, March 15–16, 2003.
© 2005 Elsevier B.V. Published by Elsevier Inc. All rights reserved.