Angelman syndrome caused by loss of a marker chromosome: cytogenetic and fluorescence in situ hybridization analysis.

We report a cytogenetic and fluorescence in situ hybridization study of a family in which a female child showed all the main characteristics of Angelman syndrome. Her karyotype revealed a translocation between chromosomes 5 and 15 with a partial deletion from 15pter to the Angelman region. Several members of her family appeared to be carriers of the same translocation, but showed no symptoms. The karyotypes showed a marker chromosome, that was not present in the female with Angelman syndrome. Fluorescence in situ hybridization revealed that the marker chromosome corresponded to material from chromosome 15. The present study is in agreement with the suggestion that genomic imprinting is one of the mechanisms involved in Angelman syndrome.