Phenotype of a patient with pure partial trisomy 2p(p23-->pter)

Duplication 2p25 in a child with clinical features of CHARGE syndrome

CHARGE syndrome is a dominant disorder characterized by ocular colobomata, heart defects, choanal atresia, retardation of growth and development, genital hypoplasia, and ear abnormalities including deafness and vestibular disorders. The majority of individuals with CHARGE have pathogenic variants in the gene encoding CHD7, a chromatin remodeling protein. Here, we present a 15-year-old girl with clinical features of CHARGE syndrome and a de novo 6.5 Mb gain of genomic material at 2p25.3-p25.2. The duplicated region contained 24 genes, including the early and broadly expressed transcription factor gene SOX11. Analysis of 28 other patients with CHARGE showed no SOX11 copy number changes or pathogenic sequence variants. To our knowledge, this child's chromosomal abnormality is unique and represents the first co-occurrence of duplication 2p25 and clinical features of CHARGE syndrome. We compare our patient's phenotype to ten previously published patients with isolated terminal duplication 2p, and elaborate on the clinical diagnosis of CHARGE in the context of atypical genetic findings.

Partial trisomy 2p and partial monosomy 2q arising from a paternal intrachromosomal 2q-into-2p between-arm insertion and paracentric inversion: molecular cytogenetic characterization of a four-break rearrangement

We report on a 26-month-old boy with an interstitial duplication of 2p22.3p22.2 and an interstitial deletion of 2q14.1q21.2. The abnormality was derived from his father having a balanced paracentric inversion and pericentric insertion. The deletion in the child was identified by cytogenetic analysis and characterized in more detail by molecular cytogenetics and array comparative genomic hybridization. The latter revealed a 20-Mb deletion in the long arm and a 5.6-Mb duplication in the short arm of chromosome 2. Fluorescence in situ hybridization in paternal chromosomes characterized an intrachromosomal insertion of 2q14.1q21.2 into 2p23; additionally a paracentric inversion of 2p13p23 was observed. The boy with the unbalanced karyotype suffered from severe psychomotor retardation, thrombophilia due to protein C deficiency, and hypertrophic cardiomyopathy and also had phenotypic abnormalities. Most of these features have previously been described in individuals with interstitial deletion of 2q14.1.

A case of partial trisomy 2p23-pter syndrome with trisomy 18p due to a de novo supernumerary marker chromosome

Partial trisomy 2p is a rare but relatively well-defined syndrome with distinctive clinical features, including marked psychomotor delay, dysmorphic face, and congenital heart disease. The phenotype of trisomy 18p is variable, from normal appearance to moderate mental retardation. Most cases of trisomy 2p and trisomy 18p result from the inheritance of an unbalanced segregant from a balanced parental translocation or due to de novo duplication. Here, we present the first report of a combined partial trisomy 2p and trisomy 18p due to a supernumerary marker chromosome (SMC). The final karyotype of the patient was 47,XX,+der(18)t(2;18)(p23.1;q11.1)[22]/46,XX[8]. The patient had typical dysmorphic features of partial trisomy 2p23-pter syndrome and congenital heart disease. SMCs are remarkably variable in euchromatic DNA content and mosaicism level. The precise identification of the origin and composition of SMCs is essential for genotype-phenotype correlation and genetic counseling.

A Partial Trisomy 2p(p21→pter) Derived from a Paternal t(2;4)(p21;q33) Karyotype

We describe a 7-year-old boy with additional material on 4q whose karyotype was 46, XY, der(4) t(2;4)(p21: q33). The father's karyotype was 46, XY, t(2;4)(p21;q33) and the mother's was normal. These results indicate that the extra material on 4q in the patient originated from the father's chromosome 2p. The patient had dysmorphic facial features, prominent ears, long fingers, developmental delay, speech delay and suffered from seizures.

Recurrent inverted duplication of 2p with terminal deletion in a patient with the classical phenotype of trisomy 2p23-pter

Inverted duplications with terminal deletions have been reported in an increasing number of chromosomes and are probably more frequent than suspected until recently. We describe the cytogenetic and molecular characterization of an inverted duplication of chromosome 2p in an 8-year-old girl. Firstly interpreted as partial duplication 2p, the rearrangement was in fact an inverted duplication associated with a terminal deletion of the short arm of the rearranged chromosome 2, the latter not being detectable by cytogenetic analysis. The complete karyotype was: 46,XX,add(2)(p23)dn.ish inv dup del(2)(:p23.2-->p25.3::p25.3-->qter) (wcp2+,N-MYC++,2pter-)dn. We precisely define the extension of both the duplication and the deletion using bacterial artificial chromosomes clones spanning the regions. The size of the inverted duplicated segment was estimated to be 28 Mb, spanning from 2p23.2 to 2p25.3, and an approximately 1.6 Mb segment at 2pter-p25.3 was deleted in the abnormal chromosome. The physical findings noted in our patient include prominent forehead, hypertelorism, flat nasal bridge, and low-set and large ears. In addition, she had congenital heart defect and scoliosis. Her psychomotor development was severely delayed from the beginning. All these clinical features are the same as observed for the typical trisomy 2p23-pter syndrome. The phenotypic effects of the terminal deletion of 2p in addition to the trisomy are discussed. This is the third patient presenting with a severe clinical phenotype and a de novo inv dup del (2p).

Unrelated patients with a rearrangement of chromosome 2 causing duplication of 2p23 and deletion of 2q37

We describe two unrelated patients who each have a similar chromosome 2 with duplication of 2p23 to pter, and deletion of 2q37 to qter. In one, the abnormality was derived from his mother with a pericentric inversion. Both individuals have frontal bossing; abnormally formed, low set and posteriorly rotated ears; redundant nuchal skin; inversion of the nipple(s); fleshy fingertips with prominent pads; a sacral dimple; significant developmental delay/mental retardation; and G-tube dependency. Most of these features are present in previously described individuals with either duplication of the 2p terminus or deletion of the 2q terminus. This report is the first that documents postnatal viability of individuals with concurrent duplication of 2p and deletion of 2q, and also generation of this imbalance through rearrangement of a maternally inherited pericentrically inverted 2. This report should be considered in the reproductive counseling of individuals with pericentric inversions of chromosome 2.

Identification of 14 rare marker chromosomes and derivatives by spectral karyotyping in prenatal and postnatal diagnosis

Extra structurally abnormal chromosomes (ESACs) and cryptic rearrangements are often associated with mental retardation and phenotypic abnormalities. In some cases their characterisation, using standard cytogenetic techniques and fluorescence in situ hybridization (FISH), is difficult and time consuming, where a fast and accurate identification is essential, especially when such chromosomal aberrations are found in prenatal diagnosis. A recent molecular technique, spectral karyotyping (SKY), based on the spectral signature of 24 chromosome-specific painting probes labelled with different combinations of five fluorochromes, allows the simultaneous visualisation of all human chromosomes in different colours. We used SKY analysis on 14 cases with rare ESACs or cryptic unbalanced rearrangements found at pre- or postnatal diagnosis. SKY analysis permitted the classification of chromosome rearrangements in all 14 cases analysed in combination with FISH analysis.