Deletion of the distal long arm of chromosome 1: a definable syndrome.

Based on analysis of 15 cases, there appears to be a characteristic facial appearance and pattern of associated malformations that would allow clinical delineation of deletion of the distal bands of 1q. Characteristic manifestations include round face with prominent "cupid's bow" and downturned corners of the mouth, thin vermilion borders of lips, long upper lip with smooth philtrum, short and broad nose, epicanthal folds, apparently low-set ears, micrognathia, microcephaly, abnormal hands and feet, variable cardiac, genital, and other anomalies, moderate to severe mental retardation, and growth retardation. The deletion includes 1q42 or 1q43----qter and was a de novo defect in nine of 15 cases.