A case of pure partial duplication 3q in a fetus due to a maternally inherited der(5)ins(5;3)(q33.1;q26.2q27) delineated by FISH

A Pure 2-Mb 3q26.2 Duplication Proximal to the Critical Region of 3q Duplication Syndrome

Partial duplication of chromosome 3q - dup(3q) - is a recognizable syndrome with dysmorphic facial features, microcephaly, digital anomalies, and genitourinary and cardiac defects, as well as growth retardation and developmental delay. Most cases of dup(3q) result from unbalanced translocations or inversions and are accompanied by additional chromosomal imbalances. Pure dup(3q) is rare, and only 31 cases have been reported so far. We report a new case of a girl with a pure 2-Mb duplication at 3q26.2 not encompassing the known critical region 3q26.3q27. After an extensive review, to the best of our knowledge, the case herein presented harbors the shortest 3q duplication of this region. The clinical phenotype of this patient resembles previously reported cases of pure dup(3q) syndrome, including intellectual disability, synophrys, a wide nasal bridge, dysmorphic ears, clinodactyly, and cardiac defects. We suggest that the 3q26.2 duplication is a candidate copy number alteration explaining our patient's clinical phenotype.

Comprehensive review of the duplication 3q syndrome and report of a patient with Currarino syndrome and de novo duplication 3q26.32-q27.2

Partial duplications of the long arm of chromosome 3, dup(3q), are a rare but well-described condition, sharing features of Cornelia de Lange syndrome. Around two thirds of cases are derived from unbalanced translocations, whereas pure dup(3q) have rarely been reported. Here, we provide an extensive review of the literature on dup(3q). This search revealed several patients with caudal malformations and anomalies, suggesting that caudal malformations or anomalies represent an inherent phenotypic feature of dup(3q). In this context, we report a patient with a pure de novo duplication 3q26.32-q27.2. The patient had the clinical diagnosis of Currarino syndrome (CS) (characterized by the triad of sacral anomalies, anorectal malformations and a presacral mass) and additional features, frequently detected in patients with a dup(3q). Mutations within the MNX1 gene were found to be causative in CS but no MNX1 mutation could be detected in our patient. Our comprehensive search for candidate genes located in the critical region of the duplication 3q syndrome, 3q26.3-q27, revealed a so far neglected phenotypic overlap of dup(3q) and the Pierpont syndrome, associated with a mutation of the TBL1XR1 gene on 3q26.32.

A unique case of a discontinuous duplication 3q26.1-3q28 resulting from a segregation error of a maternal complex chromosomal rearrangement involving an insertion and an inversion

Until now, few cases of partial trisomy of 3q due to segregation error of parental balanced translocation and segregation of a duplicated deficient product resulting from parental pericentric inversion have been reported so far. Only five cases of chromosomal insertion malsegregation involving 3q region are available yet, thus making it relatively rare. In this case report, we are presenting a unique case of discontinuous partial trisomy of 3q26.1-q28 region which resulted from a segregation error of two insertions involving 3q26.1 to 3q27.3 and 3q28 regions with ~21Mb and ~2Mb sizes, respectively. The maternally inherited insertion was cytogenetically characterized as der(8)(8pter→8p22::3q26→3q27.3::3q28→3q28::8p22→8qter) and the patient's major clinical features involved Dandy Walker malformation, sub-aortic ventricular septal defect, upslanting palpebral fissures, clinodactyly, hirsutism, and prominent forehead. Besides, a review of the literature involving cases with similar chromosomal imbalances and cases with "3q-duplication syndrome" is also provided.