Distal 8p deletion (8)(p23.1): an easily missed chromosomal abnormality that may be associated with congenital heart defect and mental retardation.

We describe the clinical manifestations and molecular cytogenetic analyses of three patients with a similar distal deletion of chromosome 8. Each child had mild developmental delay and subtle minor anomalies. Two had cardiac anomalies but no other major congenital anomalies were present. High resolution G and R banding showed in all three patients del(8)(p23.1), but the breakpoint in case 1 was distal to 8p23.1, in case 2 was in the middle of 8p23.1, and in case 3 proximal to 8p23.1. Fluorescence in situ hybridization (FISH) studies with a chromosome 8 paint probe confirmed that no other rearrangement had occurred. FISH with a chromosome 8-specific telomere probe indicated that two patients had terminal deletions. Chromosome analysis of the parents of case 1 and mother of case 2 were normal; the remaining parents were not available for study. Thirteen individual patients including the three in this study, and three relatives in one family with del(8)(p23.1), have been reported in the past 5 years. Major congenital anomalies, especially congenital heart defects, are most often associated with a breakpoint proximal to 8p23.1. Three patients were found within a 3-year period in this study and five cases were found within 4 years by another group, indicating that distal 8p deletion might be a relatively common chromosomal abnormality. This small deletion is easily overlooked (i.e., cases 1 and 2 were reported as normal at amniocentesis) and can be associated with few or no major congenital anomalies.