Interstitial deletion of chromosome 12q: genotype-phenotype correlation of two patients utilizing array comparative genomic hybridization.

Interstitial deletions of chromosome 12q are rare, with only 11 reported cases in the literature. We recently described two cases with cytogenetically identical interstitial deletions of the long arm of chromosome 12. Here, we report on a third patient, a 26-month-old male with a cytogenetically-identical interstitial deletion: 46,XY,del(12)(q21.2q22). Phenotypic features of this male proband included craniofacial and ectodermal anomalies, genitourinary anomalies, minor cardiac abnormalities, mild ventriculomegaly on brain MRI, hyperopia, and developmental delay. To further define the extent of the chromosomal aberration, microarray-based comparative genomic hybridization (array CGH) analysis was performed and the array data was compared to one of our previously reported cases. Although cytogenetic analysis of the two patients was concordant, molecular analysis by array CGH revealed that the patients had discordant distal breakpoints. The determination of molecular breakpoints and phenotypic analyses in these two patients, in conjunction with previously reported cases, leads us to propose a 12q deletion phenotype and a possible genetic locus for hyperkeratosis pilaris/ulerythema ophryogenes.