Signs in dysmorphologyThe importance of chromosome studies in Roberts syndrome/SC phocomelia and other cohesinopathies

Roberts syndrome/SC phocomelia is a rare, autosomal recessive syndrome characterised by pre- and postnatal growth retardation, microcephaly, craniofacial anomalies, mental retardation, and tetraphocomelia in varying degrees of severity. The clinical diagnosis can be challenging in phenotypically mild cases. In the extremely mild case presented here, specific mitotic abnormalities were detected and proved to be very helpful, since Roberts syndrome/SC phocomelia could be diagnosed after finding premature centromere separation and somatic aneuploidy at routine karyotyping. We discuss these and other mitotic cytogenetic abnormalities that can be of significant diagnostic importance, but which will be missed if only array studies are performed. We also discuss the difference between premature centromere separation and premature (sister) chromatid separation.