Abstract
AimClinical and molecular cytogenetic investigations of a newborn girl exhibiting facial dysmorphism with developmental delay.MethodsPhenotypic evaluation was first applied to examine the proband's developmental status. Computed tomography and colour transcranial Doppler were used then to investigate her brain structure and function. Subsequently, chromosomal abnormalities were examined by karyotyping and fluorescent in situ hybridization was performed to investigate size of fragments lost at the two distal ends of the ring chromosome 7. In addition, multicolour banding was applied to rule out structural rearrangement occurs in between the ring chromosome 7.ResultsThe proband was born with mosaic supernumerary ring chromosome 7, without a normal karyotype detected in the peripheral blood lymphocytes. The distal arm of chromosome 7p (at least 255 kb from the telomere) was part of an extra ring chromosome 7. In addition, the distal arm of 7q, at least 8 kb from the telomere, was missing. There was no other chromosomal rearrangement detected by multicolour banding.InterpretationThis is the 19th reported case of complete ring chromosome 7 mosaicism and the first survived case with mosaic supernumerary ring 7 without a normal karyotype detected in the peripheral lymphocytes.
Highlights
Ring chromosome 7 is a rare chromosome anomaly that leads to variable phenotypes
Ring chromosomes are often unstable during mitosis; it is common to find a ring chromosome in only a portion of all cells analyzed
This is the first survived case with complete supernumerary ring 7, without a normal karyotype detected in the peripheral lymphocytes
Summary
Ring chromosome 7 is a rare chromosome anomaly that leads to variable phenotypes. The first two cases were described by Zackai et al in 1973 [1]. A total of 18 cases with complete ring chromosome 7 have been reported to date worldwide [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. Ring chromosomes are often unstable during mitosis; it is common to find a ring chromosome in only a portion of all cells analyzed (mosaicism). We present the 19th case of complete ring chromosome 7 mosaicism. This is the first survived case with complete supernumerary ring 7, without a normal karyotype detected in the peripheral lymphocytes. The phenotypic expression of patients with ring chromosome 7 is
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