A French multicenter study of over 700 patients with 22q11 deletions diagnosed using FISH or aCGH.

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.

Pattern of secretion of pregnancy-associated plasma protein-A (PAPP-A) during pregnancies complicated by fetal aneuploidy, in vivo and in vitro.

BACKGROUND: Pregnancy-associated placental protein-A (PAPP-A) is a metalloprotease which circulates as an hetero-tetramer in maternal blood. Its maternal serum concentration in fetal trisomy 21 is decreased during the first trimester, so that PAPP-A is a useful screening biomarker. However, the regulation of PAPP-A placental secretion is unclear. We therefore investigated the secretion of PAPP-A in pregnancies complicated by fetal aneuploidies, both in vivo and in vitro. METHODS: Maternal serum collected between 10 WG and 33 WG during 7014 normal pregnancies and 96 pregnancies complicated by fetal trisomy 21, 18, and 13 were assayed for PAPP-A using the Immulite 2000xpi system®. The pregnancies were monitored using ultrasound scanning, fetal karyotyping and placental analysis. Villous cytotrophoblasts were isolated from normal and trisomic placenta and cultured to investigate PAPP-A secretion in vitro (n=6). RESULTS: An increased nuchal translucency during the first trimester is a common feature of many chromosomal defect but each aneuploidy has its own syndromic pattern of abnormalities detectable at the prenatal ultrasound scanning and confirmed at the fetal examination thereafter. PAPP-A levels rise throughout normal pregnancy whereas in trisomy 21, PAPP-A levels were significantly decreased, but only during the first trimester. PAPP-A levels were decreased in trisomy 13 and sharply in trisomy 18, whatever the gestational age. In vitro, PAPP-A secretion was decreased in aneuploidy, and associated with decreased hCG secretion in Trisomy 21 and 18. These biochemical profiles did not appear to be linked to any specific histological lesions affecting the placenta. CONCLUSIONS: These profiles may reflect different quantitative and qualitative placental dysfunctions in the context of these aneuploidies.

Amniocentesis performed for karyotyping after identified ultrasonographic abnormalities: what to expect?

OBJECTIVES: The aim of this study was to evaluate the relative risk of identifying fetal chromosomal anomalies after finding ultrasonographic (US) abnormalities in a high-risk population who underwent amniocentesis. METHODS: A retrospective review of a cohort of patients with single pregnancies who underwent genetic amniocentesis was undertaken. Univariate and multivariate analysis were used to determine the best correlations between US findings and chromosomal abnormalities. RESULTS: Overall, 191 chromosomal abnormalities were found in 5,604 fetuses (3.4%). Multivariate analysis showed chromosomal abnormalities were significant ly associated with anomalies of the central nervous system (OR = 4.4, 95% CI 2.2-8.7), face and neck (OR = 15.7, 95% CI 9.2-26.8), heart (OR = 5.4, 95% CI 2.6-11.2), abdomen (OR = 5.6, 95% CI 2.9-10.9), extremities (OR = 5.7, 95% CI 2.4-13.4), an increased nuchal fold (OR = 5.2, 95% CI 3.3-8.1), an intrauterine growth restriction (OR = 3.6, 95% CI 1.6-7.9) and a short femur (OR = 4.1, 95% CI 1.4-12.1). CONCLUSIONS: Our results confirm the validity of specific US markers in detecting chromosomal abnormalities in the fetus.

Intrachromosomal insertion mimicking a pericentric inversion: molecular cytogenetic characterization of a three break rearrangement of chromosome 20.

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.