Identical twins with deletion 16q syndrome: evidence that 16q12.2-q13 is the critical band region.

An interstitial deletion of the long arm of chromosome 16 has been identified in identical twins. These patients are strikingly similar phenotypically to previously reported cases of deletion 16q syndrome but differ chromosomally in that their deletion involves the 16q12.2-q13 rather than the 16q21. We propose that the 16q12.2-q13 is the "critical region" in the production of this rare but distinctive phenotype.