Two rare cases of 6p partial deletion.

Two rare cases of 6p partial deletion (6p23----pter) are described. Both patients are at or past the adolescent stage, with severe mental retardation and severe to moderate developmental retardation. Physical dysmorphic features that stand out are: short forehead, borderline microcephaly, low-set malformed ears, hyperplastic nares, dental anomalies and short terminal phalanges. The diversity of the phenotypic features has considerable variations in patients with ring of 6, apparently reflecting the relative loss of p and q arms. A case of a larger terminal deletion and a report of an interstitial deletion is also reviewed.