Monozygotic twins withchromosome 22q11 deletion anddiscordant phenotype

We reportmonozygotic twinsconcordant for22qI1.2 deletion butdiscordant for clinical phenotype. Bothboys-showthe typical dysmorphic features withshort palpebral fissures, square nasaltip,small mouth,andbothhavenasalspeech, but onlyone twinhad a heartdefect. They showthatthephenotypic variability seen inthismicrodeletion syndromecannotbe explained on thebasis ofgenotypic differences alone. (JMedGenet1995;32:746-748)