RT Journal Article SR Electronic T1 Monozygotic twins with chromosome 22q11 deletion and discordant phenotypes: updates with an epigenetic hypothesis JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP e71 OP e71 DO 10.1136/jmg.39.11.e71 VO 39 IS 11 A1 S M Singh A1 B Murphy A1 R O’Reilly YR 2002 UL http://jmg.bmj.com/content/39/11/e71.abstract AB