Epilepsy Research 67 (2005) 163–168 Short communication Angelman syndrome: Uniparental paternal disomy 15 determines mild epilepsy, but has no influence on EEG patterns Kette D. Valente a,b,* , Cintia Fridman b,c , Monica C. Varela d , C´ elia P. Koiffmann d , Joaquina Q. Andrade e , Rosi M. Grossmann e , Fernando Kok b,e , Maria J. Marques-Dias e,f a Laboratory of Clinical Neurophysiology, Institute and Department of Psychiatry, University of S˜ ao Paulo Medical School, R. Jesu´ ıno Arruda 901 Apt. 51, 04532-082 S ˜ ao Paulo, SP, Brazil b EPICHROM Project, Institute and Department of Psychiatry, University of S˜ ao Paulo Medical School, S˜ ao Paulo, SP, Brazil c Departament of Legal Medicine, University of S˜ ao Paulo Medical School, S˜ ao Paulo, SP, Brazil d Center for the Study of Human Genome, Department of Biology, University of S˜ ao Paulo Medical School, S˜ ao Paulo, SP, Brazil e Child Neurology Unit, Department of Neurology, University of S˜ ao Paulo Medical School, S˜ ao Paulo, SP, Brazil f Institute and Department of Pediatrics, University of S˜ ao Paulo Medical School, S˜ ao Paulo, SP, Brazil Received 5 April 2005; received in revised form 16 August 2005; accepted 7 September 2005 Available online 14 October 2005 Abstract The authors describe the electroclinical phenotype of four patients with Angelman syndrome (AS) determined by its rarest genetic mechanism—uniparental disomy (UPD). The analysis of ours and published patients showed that in UPD, when epilepsy occurred, it was milder compared to patients with deletion, although a suggestive EEG was observed in most patients. We found that UPD patients do not completely fit the scenario delineated for AS, suggesting that patients determined by different mechanisms should be distinctly addressed, for a better understanding of this syndrome. © 2005 Elsevier B.V. All rights reserved. Keywords: Angelman syndrome; UPD; Epilepsy; EEG; Genotype Angelman syndrome (AS) is determined by dif- ferent genetic mechanisms, affecting the maternal chromosome 15: deletion (DEL), uniparental disomy * Corresponding author. Tel.: +55 11 30795493; fax: +55 11 30795493. E-mail address: kettevalente@msn.com (K.D. Valente). (UPD), imprinting center abnormalities and UBE3A mutations. One of these, paternal UPD, occurs in 1–3% of all AS patients. Although rare, there is strong evidence of a milder phenotype in the few patients described, constituting a putative subgroup representing a challenge for clinical diagnosis (Bottani et al., 1994; Fridman et al., 2000; Gillessen-Kaesbach et al., 1995). 0920-1211/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.eplepsyres.2005.09.003