Clinical characteristics in patients with interstitial deletions of chromosome region 12q21-q22 and identification of a critical region associated with keratosis pilaris.

We report on a male patient with a submicroscopic 1.21 Mb de novo deletion at 12q21.33-q22 with global developmental delay, characteristic facial features, and keratosis pilaris. Thus far, five other cases with a 12q de novo deletion including this segment have been reported; our case represents the smallest de novo deletion within this chromosome region. High resolution SNP microarray analysis showed a deletion of RefSeq genes BTG1 and LOC256021, and partial deletion of DCN. We propose that BTG1 is a critical gene for the development of the distinctive keratosis pilaris observed in patients with interstitial deletion of 12q21-q22, and suggest candidate genes that may contribute to dysmorphic features and global developmental delay.