ROBERTS SYNDROME: CLINICAL AND CYTOGENETIC STUDIES IN 8 EGYPTIAN PATIENTS AND MOLECULAR STUDIES IN 4 PATIENTS WITH GENOTYPE/PHENOTYPE CORRELATION.

The Roberts syndrome (RBS) is a rare autosomal recessive disorder caused by mutation in ESCO2 gene. Among over 150 reported international cases, 16 cases are Egyptian including the presently reported patients. The current study reports 8 new Egyptian patients from 7 unrelated consanguineous families investigating clinical phenotype as well as cytogenetic changes in all cases and mutational spectrum in 4 cases. Clinical, orodental, cytogenetic and molecular studies were done to investigate genotype/phenotype correlation. Evaluation of the studied 8 patients showed that they all exhibited the main limb and craniofacial features of Roberts syndrome. Cytogenetic studies including centromeric separation and puffing by Giemsa and DAPI stains and for the first time in Egypt analysis for premature centromeric division by FISH showed consistent centromeric separation in all studied cases. Molecular studies of 4 available patients showed that they all have ESCO2 gene mutation. We conclude that RBS has a well-defined clinical spectrum. The cytogenetic changes are due to sister chromatid cohesion defects which lead to mitotic dysfunction. We confirmed previous results of lack of genotype/phenotype correlation. We also confirmed that the severity of limb malformation correlates with craniofacial manifestations. We recommend detailed evaluation of orodental changes for further definition of the phenotype and for proper patient management. We emphasize the need for further studies for the frequency of premature centromeric separation by FISH as a possible indicator of phenotypic severity.