Taiwanese journal of obstetrics & gynecology · 2025
Genetic analysis of a fetus with mosaic trisomy 15 with false-negative result in prenatal amniotic fluid karyotype analysis.
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Li Xiang, Peng Yuanmei, Liu Weiwu, Song Jujie, Deng Guosheng
Аннотация
OBJECTIVE: To investigate the cause of a false-negative result in prenatal amniotic fluid karyotype analysis for a fetus with mosaic trisomy 15, and to propose a cytomolecular genetic strategy for detecting mosaicism in amniotic fluid.
CASE REPORT: Amniocentesis was performed on a second-trimester pregnant woman presenting with a single umbilical artery and alpha-thalassemia carrier status. Multiplex ligation-dependent probe amplification (MLPA-P245) suggested mosaic trisomy 15, whereas conventional karyotype analysis showed a normal result. Further genetic testing, including copy number variation sequencing (CNV-seq), fluorescence in situ hybridization (FISH), and short tandem repeat (STR) analysis, was performed to exclude maternal cell contamination. MLPA-P245 revealed elevated signals for chromosome 15, indicating mosaic trisomy 15 (approximately 40-50%). CNV-seq detected an 81.83 Mb duplication in 15q11.2q26.3, consistent with ~60% mosaicism, while FISH confirmed ~8% mosaic trisomy 15. Parental karyotypes were normal. After genetic counseling, the patient chose pregnancy termination.
CONCLUSION: Cellular overgrowth during culture may lead to false-negative karyotype results in mosaic trisomy detection. A combined diagnostic approach using karyotype analysis, CNV-seq, and FISH is recommended to improve the accuracy of mosaicism detection in amniotic fluid samples.
CASE REPORT: Amniocentesis was performed on a second-trimester pregnant woman presenting with a single umbilical artery and alpha-thalassemia carrier status. Multiplex ligation-dependent probe amplification (MLPA-P245) suggested mosaic trisomy 15, whereas conventional karyotype analysis showed a normal result. Further genetic testing, including copy number variation sequencing (CNV-seq), fluorescence in situ hybridization (FISH), and short tandem repeat (STR) analysis, was performed to exclude maternal cell contamination. MLPA-P245 revealed elevated signals for chromosome 15, indicating mosaic trisomy 15 (approximately 40-50%). CNV-seq detected an 81.83 Mb duplication in 15q11.2q26.3, consistent with ~60% mosaicism, while FISH confirmed ~8% mosaic trisomy 15. Parental karyotypes were normal. After genetic counseling, the patient chose pregnancy termination.
CONCLUSION: Cellular overgrowth during culture may lead to false-negative karyotype results in mosaic trisomy detection. A combined diagnostic approach using karyotype analysis, CNV-seq, and FISH is recommended to improve the accuracy of mosaicism detection in amniotic fluid samples.