[Genetic study of a fetus with a de novo Xp22.33;Yp11.2 translocation]

To delineate cytogenetic and molecular abnormalities of a fetus carrying a de novo 46,X,der(X),t(X;Y)(p22.3;p11.2).

G-banded karyotyping and next-generation sequencing (NGS) were used to analyze the fetus, his father and sister. Single nucleotide polymorphism-based arrays (SNP-array), multiple PCR and fluorescence in situ hybridization (FISH) were utilized to verify the result.

G-banded karyotyping at 320 bands showed that the fetus had a normal karyotype, while NGS has identified a 3.58 Mb microdeletion at Xp22.33 and a Y chromosomal segment of about 10 Mb at Yp11.32p11.2. With the sequencing results, high-resolution karyotyping at 550-750 bands level has determined the fetus to be 46,X,der(X)t(X;Y)(p22.3;p11.2). The result was confirmed by PCR amplification of the SRY gene, FISH and SNP-array assays. The karyotypes of his father and sister were both normal. His sister also showed no amplification of the SRY gene, and her NGS results were normal too, suggesting that the karyotype of the fetus was de novo.

Combined karyotyping, NGS, SNP-array, PCR and FISH assay can facilitate diagnosis of XX disorder of sex development.