The phenotype of inverted duplicated 8p, region 8p11.2-p23, reported in children and adults, includes: severe mental retardation, minor facial anomalies, agenesis of corpus callosum, and other malformations including those of heart and kidneys. We report on the prenatal diagnosis of 2 cases of inverted duplication 8p. Both cases were ascertained by abnormal level 2 ultrasound findings. Case 1 presented at 16.5 weeks of gestation with massive distention of the fetal bladder, bilateral hydronephrosis, abnormality of the lower lumbar spine, absence of the sacral spine and a Dandy-Walker variant (interhemispheric cyst and enlarged third ventricle). Case 2 presented at 30 weeks of gestation with agenesis of corpus callosum, slightly enlarged lateral ventricles, interhemispheric cyst and enlarged third ventricle, and possible coarctation of the aorta. The intracranial and cardiac anomalies were confirmed and further defined after delivery. Cytogenetic analysis in both cases showed additional material on 8p. In both cases, fluorescence in situ hybridization (FISH) defined the abnormal chromosome, as a pseudodicentric chromosome with duplication of the short arm from centromere to p23 and deletion from p23 to pter. Our findings support those of prior reports of the inverted duplicated 8p chromosome with multiple anomalies and add prenatal findings to our knowledge.
We report the prenatal diagnosis, at 18 weeks' gestational age of a del(8)(p23.1-->pter) in a fetus with an atrio-ventricular canal, persistent left superior vena cava and hypoplastic right ventricle detected by sonographic imaging. We further refine the breakpoints associated with this defect using fluorescent in situ hybridization analysis (FISH). Our findings correlate with recent reports of the localization and importance of GATA4 (a zinc finger transcription factor) in cardiac development. Though microcephaly, mental retardation and typical behavioural features are well described in various deletions in 8p, the absence of notable microcephaly in this case raises the possibility for a separate genetic aetiology for some of these features. Indeed, primary autosomal recessive microcephaly (MCPH1) was recently mapped to a nearby region and may be the cause for this frequent observation in some cases of 8p deletions. These observations illustrate the role of FISH in prenatal diagnosis and refinement of chromosomal breakpoints. In addition, mappings of loci significant for cardiac development are presented. Our findings suggest that some features of the 8p deletion syndrome may ultimately be uncoupled from one another, and underscore the need for further study of this region of chromosome 8, in order to achieve adequate information for genetic counselling.
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