Molecular and Cytogenetic Characterization of a Fetus with Mosaic Ring Chromosome 13: A Very Rare Case

Prenatal diagnosis of a fetus with mosaic ring chromosome 13: Case report and review of the literature

OBJECTIVE

To diagnose the ring chromosome 13 (r(13)) in a fetus, and analyze the genotype-phenotype correlation.

CASE REPORT

A 26-year-old woman who was second pregnancy, underwent amniocentesis at 18 weeks of gestation because of the increased nuchal translucency (NT). Prenatal ultrasound showed the NT thickness was 3.5 mm at 12⁺¹ weeks of gestation and nuchal fold (NF) was 6.1 mm at 18 weeks of gestation, and amniotic fluid karyotype analysis revealed mosaic r(13). CMA detected a 16.293 Mb duplication at 13q21.32q31.1 and 31.303 Mb deletion at 13q31.1q34.

CONCLUSION

R(13) is a very rare chromosomal abnormality. Cytogenetic examination combined with CMA can provide accurate diagnosis and effective information for genetic counseling.

Lessons from a 30 year follow-up of monozygotic twins with discordant phenotype due to a ring 13 chromosomal mosaicism in one of them

At the 43rd annual meeting of the ASHG in 1993, the senior author reported monozygotic twins with discordant phenotype due to a ring 13 chromosomal mosaic syndrome in one of them. Her major manifestations included: intrauterine growth restriction (IUGR), failure to thrive (FTT), delayed developmental milestones/intellectual disability (DDM/ID), left hemihypoplasia of her body with leg length discrepancy, left profound deafness due to inner ear malformation, telecanthus, dental anomalies mainly on the left side, congenital torticollis due to Klippel-Feil anomaly, 13 ribs, scoliosis, dislocation of the left hip, and distinctive left hand and feet. A blood karyotype at age 3^1/2 was normal. Silver-Russell syndrome was initially suspected; however, at age 4, a karyotype on skin fibroblasts showed a ring 13 chromosomal mosaicism, 46,XX,15s+/46,XX,-13,+r(13),15s+, with a higher frequency on the left side of the body. Since then, we have been involved in the management of this patient for 30 years. This has ultimately allowed us to compare her achievements with her normal monozygotic twin. In this long term follow-up, we want to emphasize the importance of: (a) early recognition of genetic syndromes, especially of mosaicisms, and of early intervention programs, (b) the involvement of different specialists in the management of patients with MCA, and (c) mentioning how familial and socioeconomic issues may limit or enhance the full potential of patients with some genetic disorders.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for r(13), monosomy 13 and idic r(13) by amniocentesis

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for ring chromosome 13 [r(13)], monosomy 13 and isodicentric ring chromosome 13 [idic r(13)] by amniocentesis.

CASE REPORT

A 24-year-old woman underwent amniocentesis at 23 weeks of gestation because of intrauterine growth restriction (IUGR) in the fetus. Amniocentesis revealed a karyotype of 46,XY,r(13)[23]/45,XY,-13[10]/46,XY,idic r(13)[2]. The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) on cultured amniocytes revealed the result of arr 13q11q31.3 (19,436,286-92,284,309) × 1.85, arr 13q31.3q34 (92,288,514-115,107,733) × 1 [GRCh37 (hg19)], indicating a 22.82-Mb 13q31.3-q34 deletion and a 15-20% mosaicism for 13q11-q31.3 deletion. The pregnancy was subsequently terminated, and a malformed fetus was delivered with facial dysmorphism. The placental tissues had a karyotype of 46,XY,r(13)[18]/46,XY,-13,+mar[14]/45,XY,-13[8]. Polymorphic DNA marker analysis confirmed a maternal origin of the 13q deletion.

CONCLUSION

Fetus with mosaic r(13), monosomy 13 and idic r(13) may present IUGR on prenatal ultrasound, and fetoplacental cytogenetic discrepancy may exist under such a circumstance.

[Clinical and genetic features of ring chromosome 13 syndrome: an analysis of one case]

A girl aged 5 months was admitted due to developmental delay. Physical examination showed delayed physical development, unusual facies (microcephalus, hypertelorism, low-set ears, wide nasal bridge, and short philtrum), and an absence of the labium minus at one side. The peripheral blood karyotype was 46,XX,r(13)(p11q33)[82]/45,XX,-13[10]/46,XX,r(13;13)(p11q33;p11q33)[8], and array-based comparative genomic hybridization showed an 87.5 Mb duplication in 13q11q33.2 region and an 8.2 Mb deletion in 13q33.2q34 region. Fluorescence in situ hybridization showed terminal depletion of the long arm of the ring chromosome 13. The girl was diagnosed with ring 13 syndrome. This syndrome has various clinical phenotypes and is closely associated with the amount and site of the loss of genetic material in chromosomal band and different rates of chimerism.