Hirschsprung disease (HSCR) is a common malformation of neural-crest-derived enteric neurons that is frequently associated with other congenital abnormalities. The SMADIP1 gene recently has been recognized as disease causing in some patients with 2q22 chromosomal rearrangement, resulting in syndromic HSCR with mental retardation, with microcephaly, and with facial dysmorphism. We screened 19 patients with HSCR and mental retardation and eventually identified large-scale SMADIP1 deletions or truncating mutations in 8 of 19 patients. These results allow further delineation of the spectrum of malformations ascribed to SMADIP1 haploinsufficiency, which includes frequent features such as hypospadias and agenesis of the corpus callosum. Thus, SMADIP1, which encodes a transcriptional corepressor of Smad target genes, may play a role not only in the patterning of neural-crest-derived cells and of CNS but also in the development of midline structures in humans.

Nine hundred and thirty-six prenatal chromosomal analyses were performed by four cytogenetic centres after ultrasound diagnosis of fetal abnormalities, amniotic fluid disorders, fetal growth retardation, and fetal or placental abnormalities. During the same period, 6515 fetal karyotypes were analysed because of maternal age. Frequencies of chromosomal aberrations in each case were respectively 4.4, 6.7 and 15.8 per cent, compared with 3.18 per cent when the fetal karyotype was performed because of maternal age. High rates of chromosomal aberrations are observed in cases of cervical hygroma, limb abnormalities, omphaloceles, duodenal stenosis, hydrocephalus, and facial abnormalities. In the case of polymalformations, this rate was 29.2 per cent. When malformations were seen together with an amniotic fluid disorder or growth retardation, 21.5 per cent chromosomal aberrations were observed. This frequency was 10.4 per cent when growth retardation was associated with an amniotic fluid disorder. Trisomy 13, 18, 21 and monosomy X accounted for 4/5 of all abnormalities in which we observed a high rate of triploidies (4.9 per cent) and balanced (3.3 per cent) or unbalanced (9.8 per cent) non-Robertsonian structural abnormalities. Sonographic ascertainment of these aberrations and prenatal characteristics of major anomalies are discussed.

Although 22q11.2 deletion syndrome (22q11.2DS) is the most recurrent human microdeletion syndrome associated with a highly variable phenotype, little is known about the condition's true incidence and the phenotype at diagnosis. We performed a multicenter, retrospective analysis of postnatally diagnosed patients recruited by members of the Association des Cytogénéticiens de Langue Française (the French-Speaking Cytogeneticists Association). Clinical and cytogenetic data on 749 cases diagnosed between 1995 and 2013 were collected by 31 French cytogenetics laboratories. The most frequent reasons for referral of postnatally diagnosed cases were a congenital heart defect (CHD, 48.6%), facial dysmorphism (49.7%) and developmental delay (40.7%). Since 2007 (the year in which array comparative genomic hybridization (aCGH) was introduced for the routine screening of patients with intellectual disability), almost all cases have been diagnosed using FISH (96.1%). Only 15 cases (all with an atypical phenotype) were diagnosed with aCGH; the deletion size ranged from 745 to 2904 kb. The deletion was inherited in 15.0% of cases and was of maternal origin in 85.5% of the latter. This is the largest yet documented cohort of patients with 22q11.2DS (the most commonly diagnosed microdeletion) from the same population. French cytogenetics laboratories diagnosed at least 108 affected patients (including fetuses) per year from among a national population of ∼ 66 million. As observed for prenatal diagnoses, CHDs were the most frequently detected malformation in postnatal diagnoses. The most common CHD in postnatal diagnoses was an isolated septal defect.

Intrachromosomal insertions are uncommon rearrangements, in which a chromosomal segment is intercalated into another part of the same chromosome. The insertion may occur in the same arm (paracentric) or in the other arm (pericentric). The cytogenetic recognition of these structurally rearranged chromosomes can be difficult, and intrachromosomal insertions can be easily mistaken for inversions. We describe a case of a familial pericentric insertion of chromosome 20, initially misdiagnosed as a pericentric inversion in the healthy carrier and then reinterpreted as insertion in an abnormal child with a recombinant chromosome. Fluorescence in situ hybridization (FISH) allowed us to confirm the mechanism of recombinant formation and to locate the three breakpoints precisely. Our cytogenetically unbalanced epileptic patient carried a 20q deletion and 20p duplication, and the genes, CHRNA4 and KCNQ2 that have been implicated in autosomal dominant epilepsy, were deleted. The haplo-insufficiency of these two genes may contribute to the cause of epilepsy in patients with ring chromosome 20.

The pregnancy termination rate declined markedly over time, from 46.9% before 1997 to 11.6% thereafter, in line with the introduction of new legislation on prenatal diagnosis for medical reasons and, more specifically, the creation of multidisciplinary prenatal diagnosis centers. However, an additional microdeletion in one KS infant who exhibited echogenic bowel on US was unfortunately diagnosed postnatally. This raises the question as to whether array comparative genomic hybridization should be prenatally advised when US abnormalities are detected, in line with advice for fetuses with a normal karyotype.