Postnatal diagnosis of 9q interstitial imbalances involving PTCH1, resulting from a familial intrachromosomal insertion

Xp22.33p22.13 Duplication in a Male Patient Carrying a Recombinant X Chromosome Derived from an Inherited Intrachromosomal Insertion

Intrachromosomal insertions are complex structural rearrangements that are challenging to interpret using classical cytogenetic methods. We report a male patient carrying a recombinant X chromosome derived from a maternally inherited intrachromosomal insertion. The patient exhibited developmental delay, intellectual disability, behavioral disorder, and dysmorphic facial features. To accurately identify the rearrangements in the abnormal X chromosome, additional cytogenetic studies were conducted, including fluorescence in situ hybridization (FISH), multicolor-banding FISH, and array comparative genomic hybridization. The results showed a recombinant X chromosome, resulting in a 13.05 Mb interstitial duplication of segment Xp22.33-Xp22.13, which was inserted at cytoband Xq26.1. The duplicated region encompasses 99 genes, some of which are associated with the patient's clinical manifestations. We propose that the combined effects of the Xp-duplicated genes may contribute to the patient's phenotype.

Two familial intrachromosomal insertions with maternal dup(6)(p22.3p25.3) or dup(2)(q24.2q32.1) in recombinant offspring

In this study, we describe two patients with a recombinant chromosome secondary to a maternal intrachromosomal insertion. Patient 1 was a girl with dup(6)(p22.3p25.3). Patient 2 was a boy with dup(2)(q24.2q32.1). Both familial rearrangements were characterized by means of GTG-bands, fluorescence in-situ hybridization, and comparative genomic hybridization microarray analyses. Patient 1 had an ∼23 Mb gain that involved the bands 6p22.3-6p25.3. Patient 2 had an ∼23 Mb gain (cytobands 2q24.2-2q32.1) and a further ∼1.9 Mb gain of 2p16.2-p16.3. The phenotype of each patient was in agreement with the typical 6p duplication or 2q24.2q32.1 duplication syndrome. The compound macular lesion in patient 1 suggests that retinal anomalies may be a part of the 6p trisomy phenotype. Among the 70 intrachromosomal insertions compiled here (including 68 from the literature), four were submicroscopic unbalanced insertions inherited from a balanced carrier and 66 were detectable on banded chromosomes (with or without array comparative genomic hybridization or other high-resolution assessment) and therefore spanned at least 5 Mb. Pericentric insertions are found in most chromosomes, whereas the paracentric ones are mainly observed in large and medium chromosome arms. That the former outnumber the latter in almost a 2 : 1 ratio appears to be related to the technique of diagnosis, size of the insertion, and size of the involved chromosome. Regardless of the apparent excess of carrier mothers, carriers of an intrachromosomal insertion beget almost twice as many children with a duplication than with a deletion.