TBX1 and 22q11.2 deletion syndrome: They concluded that deletions covering the whole TDR or the proximally nested 1.5 Mb segment result in a phenotype characterized by conotruncal CHDs and typical VCFS, mainly by effects of haploinsufficiency of TBX1, a gene previously involved in the expression of these features when mutated [26], whereas distally nested deletions including CRKL would present with a milder, atypical phenotype with uncommon CHDs, developmental delay and mental impairment.