A familial case of 22q11.2 microdeletion is reported in monozygotic twins girls and their mother. Microdeletion was confirmed by fluorescent in situ hybridisation analysis using Vysis probe. Confirmation of the monozygozity of the twins was done by PCR and STR DNA analysis. Clinical features show a broad variability in the family. Themother has typical DiGeorge syndrome phenotype (short stature, facial stigmatisation, mental defect, hypacusis) but no congenital heart defect is present. She had 3 pregnancies. The first ended with spontaneous abortion in the first trimester. From the second pregnancy a girl was born but she died at the age of 16 days due to a congenital heart defect (atresia of the pulmonary artery, ventricular septal defect, right aortic arch). Facial stigmatisation and also anal atresia were present. Although molecular cytogenetic analysis was not performed, the child’s phenotypic features raised suspicion of 22q11.2 microdeletion. The monozygotic twins are fromthe third pregnancy. They are discordant for the type of congenital heart defect and the phenotype in neonatal age. Phenotype variability in patients with 22q11 microdeletion is repeatedly described. Authors present this case to emphasize the pleiotropic effect ofmicrodeletion and the necessity of searching for familial cases to ensure genetic prevention in these families.

        Key words: microdeletion 22q11, monozygotic twins, intrafamilial phenotypic differences