Chromosome r(10)(p15.3q26.12) in a newborn child: case report

Abstract

Background: 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. 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.

Results: We 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.

Conclusion: This 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.

Figure 1

Facial features of the proband in the newborn period.

Figure 2

Malformed "rocker bottom" feet.

Figure 3

Karyotype with ring chromosome 10 replacing one normal homologue.

Figure 4

Microarray hybridization for high-resolution mapping of break points on ring chromosome 10. Copy number loss "partial monosomy" was recorded for the short arm of Chr 10: (0-) 148,946 - 281,134, corresponding to cytobands 10pter-> p15.3. An enlarged insert with the corresponding CNAG copy number analysis results presented as a table is shown above. A larger terminal deleted region is seen on the right hand side (i.e. loss of 1 copy) of the long arm of Chr 10: 122,736,794 - 135,259,604, which corresponds to cytoband 10q26.12->qter. The SNP analysis shown below the chromosome 10 ideogram indicates loss of heterozygosity in this region (straight blue bar at bottom right), confirming the copy number results.