SUBMICROSCOPIC DELETIONS AT 16P13.3 IN RUBINSTEIN-TAYBI SYNDROME - FREQUENCY AND CLINICAL MANIFESTATIONS IN A NORTH-AMERICAN POPULATION

Rubinstein-Taybi syndrome (RTS) is a well delineated multiple congenit al anomaly syndrome characterised by mental retardation, broad thumbs and toes, short stature, and specific facial features. The recent loca lisation of the disorder to 16p13.3 and subsequent identification of a submicroscopic deletion of this region in RTS patients led us to scre en a large cohort of affected subjects using the RT1 probe. Among 64 p atients with clinical evidence of RTS, seven (11%) had a deletion. Ano ther patient had a translocation of the region without evidence of a d eletion. The features growth retardation, and hypotonia have a positiv e predictive value for the presence of an RT1 deletion. Because of the relatively low frequency of deletions in RTS, the RT1 probe is useful in diagnostic confirmation, but has limited use as a screening tool.