Combined Dup(7)(q22.1q32.2), Inv(7)(q31.31q31.33), and Ins(7;19)(q22.1;p13.2p13.2) in a 12-year-old boy with developmental delay and various dysmorphism

Abstract

De novo combined duplications/inversions are very rare chromosomal rearrangements. For chromosome 7 just some dozen cases of duplications of various parts of the long arm have been published. We report on a 12-year-old boy with muscular hypotonia, global developmental delay, short stature, and various facial dysmorphism including frontal bossing, temporal narrowing, slightly down-slanting palpebral fissures, a broad nasal root, a long philtrum, a thin and tented upper lip, a drooping lower lip, micrognathia, prominent ears, a short neck, and a low posterior hairline. Karyotype analysis and molecular investigations revealed a complex de novo chromosomal rearrangement on 7q. FISH analysis with locus specific YACs and BACs and SNP array with the Illumina® HumanOmni1-Quad v1.0 BeadChip disclosed a direct duplication in the long arm of chromosome 7 (q22.1→q32.2) and an inversion located at the breakpoint between the two copies of the duplication (q31.31→q31.33). In addition, breakpoint characterization at the molecular level revealed a 386bp insertion carrying two Alu elements of chromosome 19p13.2 between the two copies of the duplication. By a comparison of the SNP haplotypes of the derivative chromosome of the patient and both parents a two-step formation during spermatogenesis was suggested as the most likely mechanism of formation.