Delineation of a duplication map of chromosome 3q: a new case confirms the exclusion of 3q25-q26.2 from the duplication 3q syndrome critical region.

We report on the clinical, cytogenetic, and molecular characterization of a propositus and his mother with a duplication of 3q25-q26, minor anomalies, and mental retardation. The duplication, detected by cytogenetic analysis, was confirmed and delineated by comparative genomic hybridization and fluorescence in situ hybridization using probes previously mapped to the region. Comparison of the mapping data obtained in these patients and those obtained in patients that present with a typical dup(3q) syndrome phenotype shows that the segment duplicated in these patients lies proximally to the reported dup(3q) syndrome critical region, thus explaining the absence in our patients of the characteristic phenotype of dup(3q) syndrome patients. Accumulation of mapping data in patients with segmental duplications of 3q will eventually allow us to build a duplication map of the region and a genotype-phenotype correlation.