Abstract
BackgroundRing chromosome 10 is a rare cytogenetic finding. Of the less than 10 reported cases we have found in the literature, none was characterized using high-resolution microarray analysis. Ring chromosomes are frequently unstable due to sister chromatid exchanges and mitotic failures. When mosaicism is present, the interpretation of genotype-phenotype correlations becomes extremely difficult.ResultsWe report on a newborn girl with growth retardation, microcephaly, congenital heart defects, dysmorphic features and psychomotor retardation. Karyotyping revealed a non-mosaic apparently stable ring chromosome 10 replacing one of the normal homologues in all analyzed metaphases. High-resolution oligonucleotide microarray analysis showed a de novo approximately 12.5 Mb terminal deletion 10q26.12 -> qter and a corresponding 285 kb terminal deletion of 10pter -> p15.3.ConclusionThis case demonstrates that an increased nuchal translucency thickness detected by early ultrasonography should preferably lead to not only QF-PCR for the diagnosis of Down syndrome but also karyotyping. In the future, microarray analysis, which needs further evaluation, might become the method of choice. The clinical phenotype of our patient was in agreement with that of patients with a terminal 10q deletion. For the purpose of genotype-phenotype analysis, there seems to be no need for a "ring syndrome" concept.
Highlights
Ring chromosome 10 is a rare cytogenetic finding
It seems likely that patients with nearly full length ring chromosomes 10 having lost e.g. the distal part of the long arm of the chromosome will have a phenotype similar to that seen in patients with terminal deletion of chromosome 10q as reviewed in Courtens et al [8]
Break points were difficult to assign but the results indicated a deletion of the distal part of the long arm of chromosome 10 in the ring formation
Summary
Ring chromosome 10 is a rare cytogenetic finding. Of the less than 10 reported cases we have found in the literature, none was characterized using high-resolution microarray analysis. It seems likely that patients with nearly full length ring chromosomes 10 having lost e.g. the distal part of the long arm of the chromosome will have a phenotype similar to that seen in patients with terminal deletion of chromosome 10q as reviewed in Courtens et al [8]. It remains to be found out whether ring chromosome phenotypes are (page number not for citation purposes)
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