[Genetic analysis of a case with mosaicism of a small supernumerary marker chromosome derived from idic(15)].

Objective: To determine the origin of a mosaicism small supernumerary marker chromosome (sSMC) by cytogenetic and molecular analysis.

Methods: Karyotype analysis, fluorescence in situ hybridization (FISH) and SNP-array were carried out.

Results: The karyotype of the patient was mos47,XX,+mar[45]/48,XX,+2mar[3]/46,XX[52]; the SNP-array result was arr[hg19]15q11.1q11.2 (20 161 372-24 314 675)×3, and the repeat fragment was about 4.15 Mb. FISH showed that approximately 50% of the cells have contained a sSMC with double D15Z1 probe site segments derived from abnormal idic(15). This sSMC did not contain SNRPN and PML probe fragments of Prader-Willi syndrome/Angelman syndrome.

Conclusion: When the patient's karyotype and phenotype are inconsistent, cytogenetic and molecular biology technologies should be combined to clarify the karyotype and gene location, so as to provide more accurate genetic consultation for the follow-up treatments.