Monozygotic twins with 22q11 deletion and discordant phenotypes.

I was interested to read the report of Goodship et al (J Med Genet 1995;32:746-8) of monozygotic (MZ) twins with a 22ql deletion who were discordant for cardiac defects. I have recently met a similar family where all the affected members have had a 22ql deletion detected by FISH. Twin 1 has a typical facial appearance of the velocardiofacial syndrome (figure) with nasal speech but no cardiac defect detectable clinically or on ECG. Twin 2 required a pharyngoplasty for nasopharyngeal insufficiency and had surgery for anASD during childhood. She has a very similar facies and both had mild learning difficulties during childhood.