Severe Saethre-Chotzen syndrome in an infant with a complex chromosome rearrangement

Abstract

Saethre-Chotzen syndrome (SCS) is an autosomal dominant craniosynostosis syndrome with variable expression. Analysis of chromosome translocations found in patients with SCS played an important role in mapping the SCS gene to 7p21 and the subsequent identification of the TWIST gene. SCS has been associated with point mutations within the TWIST gene as well as deletion of the entire gene. The purpose of this report is to present a patient with severe craniofacial features of SCS who has a complex chromosome anomaly.The patient was a product of a term gestation complicated by fetal ventriculomegaly and oligohydramnios. Physical examination in the neonatal period revealed cranial and facial asymmetry, brachycephaly, low posterior and anterior hairlines, midface hypoplasia, ptosis, broad thumbs and toes, and cryptorchidism. Imaging demonstrated bilateral coronal suture fusion, dilated lateral ventricles, partial agenesis of the corpus callosum, and a large cisterna magna. An echocardiogram revealed a VSD and ASD. At two months of age the infant had a bifrontal craniotomy and bilateral orbito-zygomatico-temporal osteotomies. At three months of age he appears to be developmentally delayed.The infant has a balanced four-way translocation between 1q, 2q, 7p, and 18p and a separate translocation between 7q and 18q. Parental karyotypes are normal. Successive FISH analyses using dual color whole chromosome paints, centromeric alpha satellite probes, and a telomeric probe for 18p confirmed these findings. The breakpoint on the short arm of chromosome 7p is assigned to 7p 15.3 and does not appear to interrupt band 7p21. Sequencing of the TWIST gene and FISH analysis using a probe specific for the TWIST region were normal. Southern blot analysis to assess dosage of the TWIST gene is pending. Mutation analysis of the FGFR genes and comparative genomic hybridisation are planned.It is possible that this infant's phenotype is the result of position effect on the TWIST gene or disruption of other genes associated with craniosynostosis This expanded cytogenetic and molecular armamentarium may allow us to determine the pathogenesis of this infant's condition and may provide further insight into the mechanisms for SCS.