Partial proximal trisomy 14: identification and molecular characterization in a girl with global developmental delay

Chromosomal rearrangements associated with a disease play a significant role in the phenotypic manifestation. Here we report a 9-month-old girl with de novo partial proximal trisomy 14 with seizures and global developmental delay. Cytogenetic investigations revealed a karyotype of 47,XX+marker. The marker was approximately the size of G-group chromosomes and almost mistaken as chromosome 22 due to its banding pattern but the trisomy 22 was ruled out considering its lethality. To find out the origin of the marker chromosome, Spectral karyotyping (SKY) was performed which showed the marker to be of chromosome 14 origin. Further Molecular cytogenetic analysis with whole chromosome 14 confirmed the marker as a derivative 14. Fluorescence in situ hybridization (FISH) with centromeric probe 14 also showed 3 signals. Further fine mapping with three Bacterial Artificial Chromosome clones helped us to tentatively find the extent of the break point regions. The use of SKY and FISH permitted the characterization of this cytogenetic abnormality. The clinical data of the present case are compared with other published cases in the literature. This helps in better genetic counseling and also in the genotype/phenotype correlation. The impact of the extra chromosomal part in relation with the phenotype of the patient is also discussed.