Two Abnormal Cell Lines of Trisomy 14 and t(X;14) with Skewed X-Inactivation.

Trisomy 14 is incompatible with live, but there are several patients reported with mosaic trisomy 14. We aimed to study the pattern of X inactivation and its effect on a translocated autosome and to find out an explanation of the involvement of chromosome 14 in 2 different structural chromosomal abnormalities. We report on a girl with frontal bossing, hypertelorism, low-set ears, micrognathia, cleft palate, congenital heart disease, and abnormal skin pigmentations. The patient displayed iris, choroidal, and retinal coloboma and agenesis of the corpus callosum and cerebellar vermis hypoplasia. Cytogenetic analysis revealed a karyotype 45,X,der(X)t(X;14)(q24;q11)[85]/46,XX,rob(14;14)(q10;q10),+14[35]. Array-CGH for blood and buccal mucosa showed high mosaic trisomy 14 and an Xq deletion. MLPA detected trisomy 14 in blood and buccal mucosa and also showed normal methylation of the imprinting center. FISH analysis confirmed the cell line with trisomy 14 (30%) and demonstrated the mosaic deletion of the Xq subtelomere in both tissues. There was 100% skewed X inactivation for the t(X;14). SNP analysis of the patient showed no region of loss of heterozygosity on chromosome 14. Also, genotype call analysis of the patient and her parents showed heterozygous alleles of chromosome 14 with no evidence of uniparental disomy. Our patient had a severe form of mosaic trisomy 14. We suggest that this cytogenetic unique finding that involved 2 cell lines with structural abnormalities of chromosome 14 occurred in an early postzygotic division. These 2 events may have happened separately or maybe there is a kind of trisomy or monosomy rescue due to dynamic cytogenetic interaction between different cell lines to compensate for gene dosage.