Objective: To explore the origin of a supernumerary small marker chromosome (sSMC) in a fetus, and to assess the feasibility of single nucleotide polymorphism array (SNP-array) for prenatal diagnosis.
Methods: The fetal sample was subjected to karyotyping analysis. The identified sSMC was subjected to genome-wide scan using a SNP microarray chip. The results were validated with fluorescence in situ hybridization (FISH).
Results: The karyotype of the fetus was determined as 47,XX,+mar, which was verified by SNP microarray chip analysis as a 34.6 Mb duplication in 12p13.33p11.1. FISH analysis confirmed that the sSMC has originated from chromosome 12p.
Conclusion: The karyotype of the fetus was determined as 47,XX,+i(12)(p10). Tetrasomy 12p is reported to be a marker for Pallister-Killian syndrome, which may result in multi-system anomalies. SNP-array analysis can simultaneously detect microdeletions and microduplications, which may be used for prenatal diagnosis of suspected cases.