Molecular cytogenetics of a de novo interstitial deletion of chromosome arm 6q in a developmentally normal girl.

Using fluorescence in situ hybridization and microsatellite analysis, we have characterized a de novo interstitial deletion on the long arm of chromosome 6 [46,XX,del(6) (q23.3q24.2)] in a developmentally normal girl with very mild phenotypic abnormalities. The deletion was paternal in origin and was between markers WI-5023 and D6S1042. The size of the deletion was estimated to be approximately 4-5 Mb. The normal phenotype in this patient might be the result of imprinting of paternal copies of genes located in the segment 6q23. 3-q24.2. Alternatively, the genes located in the segment 6q23.3-q24. 2 might not be subject to dosage effects and therefore the haploinsufficiency of genes in this segment might not have phenotypic consequences.