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. Keywords: Amniocentesis, idic r(13), Monosomy 13, Mosaicism, Ring chromosome 13