Further audiovestibular characterization of DFNB77, caused by deleterious variants in LOXHD1, and investigation into the involvement of Fuchs corneal dystrophy.

This study focuses on further characterization of the audiovestibular phenotype and on genotype-phenotype correlations of DFNB77, an autosomal recessive type of hearing impairment (HI). DFNB77 is associated with disease-causing variants in LOXHD1, and is genetically and phenotypically highly heterogeneous. Heterozygous deleterious missense variants in LOXHD1 have been associated with late-onset Fuchs corneal dystrophy (FCD). However, up to now screening for FCD of heterozygous carriers in DFNB77 families has not been reported. This study describes the genotype and audiovestibular phenotype of 9 families with DFNB77. In addition, carriers within the families were screened for FCD. Fifteen pathogenic missense and truncating variants were identified, of which 12 were novel. The hearing phenotype showed high inter- and intrafamilial variation in severity and progression. There was no evidence for involvement of the vestibular system. None of the carriers showed (pre-clinical) symptoms of FCD. Our findings expand the genotypic and phenotypic spectrum of DFNB77, but a clear correlation between the type or location of the variant and the severity or progression of HI could not be established. We hypothesize that environmental factors or genetic modifiers are responsible for phenotypic differences. No association was found between heterozygous LOXHD1 variants and the occurrence of FCD in carriers.

Clinical utility of non-invasive prenatal testing in pregnancies with ultrasound anomalies.

OBJECTIVE: To evaluate the application of non-invasive prenatal testing (NIPT) as an alternative to invasive diagnostic prenatal testing in pregnancies with abnormal ultrasound findings. METHODS: This was a retrospective analysis of 251 singleton and multiple pregnancies at high risk for fetal chromosomal abnormality based on findings at sonographic examination, in which NIPT was performed as a first-tier genetic test. NIPT was performed by massively parallel sequencing of cell-free DNA in maternal plasma, allowing genome-wide detection of whole-chromosome, as well as partial, autosomal aneuploidy. Sex chromosomes were not analyzed, according to the current protocol in Dutch laboratories. RESULTS: NIPT was performed at a median gestational age of 20 weeks, indicated by the presence of multiple congenital anomalies (n = 13), isolated structural anomalies (n = 57), increased nuchal translucency ≥ 3.5 mm (n = 58), soft markers (n = 73), growth restriction (n = 40) and other anomalies (n = 10). NIPT results were normal in 224 (89.2%) pregnancies, inconclusive in one (0.4%) and abnormal in 26 (10.4%). Most genetic aberrations detected by NIPT were common whole-chromosome aneuploidies: trisomy 21 (n = 13), trisomy 18 (n = 6) and trisomy 13 (n = 3). Four further NIPT results were abnormal; one was suspected of being confined placental mosaicism and one was of maternal origin. In those with normal NIPT results, sonographic follow-up or examination of the newborn indicated the need for diagnostic genetic testing in 33/224 (14.7%) pregnancies. Clinically relevant genetic aberrations were revealed in 7/224 (3.1%) cases, two of which were whole-chromosome aneuploidies: trisomy 13 and monosomy X. As sex chromosomal aberrations are not included in NIPT analysis, the latter cannot be considered a false-negative result. Other discordant findings were subchromosomal aberrations (< 20 megabases, n = 2) and monogenic aberrations (n = 3). CONCLUSIONS: NIPT should not be recommended for genetic evaluation of the etiology of ultrasound anomalies, as both resolution and sensitivity, or negative predictive value, are inferior to those of conventional karyotyping and microarray analysis. Nonetheless, some pregnant women consider NIPT to be an acceptable alternative to invasive diagnostic testing. © 2016 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Patient experiences with gene panels based on exome sequencing in clinical diagnostics: high acceptance and low distress.

The Radboud University Medical Center was among the first to implement two-step exome sequencing in clinical genetic diagnostics. This study is the first to evaluate patient experiences with gene panels based on exome sequencing, using quantified psychological variables: acceptance, psychological distress, expectations of heredity and unsolicited findings. Between August 2011 and July 2012, 177 patients diagnosed with early-onset colorectal/kidney cancer, deafness, blindness or movement disorder consented to diagnostic exome sequencing offered by clinical geneticists. Baseline questionnaires were sent to 141 adults, returned by 111 with median age of 49 [22-79] years and positive family history in 81%. Follow-up included 91 responders at median 4 [2-22] weeks after results from known gene panels per diagnosis group; exome-wide analysis is ongoing. Confirmed or possibly pathogenic mutations were found in 31% with one unsolicited finding (oncogenetic panel). Most patients (92%) were satisfied. There were no significant changes in heredity-specific distress (18% at baseline, 17% at follow-up) and expectations of heredity. Fewer patients expected unsolicited findings at follow-up (29% vs 18%, p = 0.01). Satisfaction and distress were equal in those with vs without mutations. In conclusion, most adults accepted and were satisfied with gene panels based on diagnostic exome sequencing, few reporting distress.

Genotype phenotype correlations for hearing impairment: approaches to management.

Hearing impairment is an extremely heterogeneous disorder, with both environmental as well as genetic causes. This review describes the known genes involved in non-syndromic hearing impairment and their genotype-phenotype correlations where possible. Furthermore, some of the more frequent syndromic forms of hearing impairment are described, in particular where they overlap with the non-syndromic forms. Given the heterogeneity of the disorder, together with the indistinguishable phenotypes for many of the genes, it is suggested that testing for mutations is performed using massive parallel sequencing techniques, either by a large targeted set of genes or by an exome wide analysis.

Globozoospermia revisited.

Globozoospermia is a rare (incidence <0.1%) but severe disorder in male infertility. Total globozoospermia is diagnosed by the presence of 100% round-headed spermatozoa lacking an acrosome. It is still unclear whether patients whose ejaculate contains both normal and globozoospermic cells (partial globozoospermia) suffer from a variation of the same syndrome. Apart from the fact that affected males suffer from reduced fertility or even infertility, no other physical characteristics can be associated with the syndrome. ICSI is a treatment option for these patients, although low fertilization rates after ICSI show a reduced ability to activate the oocyte. In globozoospermic cells, the use of acrosome markers has demonstrated an absent or severely malformed acrosome. Chromatin compaction appears to be disturbed but is not consistently over- or undercondensed. In some cases, an increased number of cells with DNA fragmentation have been observed. The analysis of the cytogenetic composition revealed an increased aneuploidy rate in some cases. Nonetheless, no increased number of spontaneous abortions or congenital defects has been reported in pregnancies conceived after ICSI. The pathogenesis of globozoospermia most probably originates in spermiogenesis, more specifically in acrosome formation and sperm head elongation. In several knockout mouse models, a phenotype similar to that in humans was found. Together with the occurrence of affected siblings, these findings indicate a genetic origin, which makes globozoospermia a good candidate for genetic analysis. More research is needed to elucidate the pathogenesis of human globozoospermia to further understand globozoospermia as well as (abnormalities in) spermiogenesis and spermatogenesis in general.

Neuropsychiatry and deletions of 18q; case report and diagnostic considerations.

The 18q deletion syndrome can be caused by several terminal and interstitial deletions of which terminal deletions of the distal part of 18q are the most frequent and known as the DeCroughy syndrome. The neuropsychiatric phenotype is not well documented and includes disorganised and disinhibited behaviours as well as language difficulties. Non development of language seems to be specific for cases with a more proximally located interstitial deletions. In the present paper a 18-year-old severely mentally retarded male with an interstitial deletion of 18q is described (46.XY,del(18)(q12.1q22.1) who was referred for behavioural problems and neuropsychiatric evaluation. No categorical psychiatric diagnosis could be established. Given this and other reports, it is advocated to describe the psychopathological phenotype of 18q deletions in a dimensional way that will result in a clinical picture characterised mainly by symptoms from the motor and motivation domains. Treatment should include primarily behavioural measures, combined if necessary with symptomatic psychopharmacotherapy.

Cytogenetic genotype-phenotype studies: improving genotyping, phenotyping and data storage.

High-resolution molecular cytogenetic techniques such as genomic array CGH and MLPA detect submicroscopic chromosome aberrations in patients with unexplained mental retardation. These techniques rapidly change the practice of cytogenetic testing. Additionally, these techniques may improve genotype-phenotype studies of patients with microscopically visible chromosome aberrations, such as Wolf-Hirschhorn syndrome, 18q deletion syndrome and 1p36 deletion syndrome. In order to make the most of high-resolution karyotyping, a similar accuracy of phenotyping is needed to allow researchers and clinicians to make optimal use of the recent advances. International agreements on phenotype nomenclature and the use of computerized 3D face surface models are examples of such improvements in the practice of phenotyping patients with chromosomal anomalies. The combination of high-resolution cytogenetic techniques, a comprehensive, systematic system for phenotyping and optimal data storage will facilitate advances in genotype-phenotype studies and a further deconstruction of chromosomal syndromes. As a result, critical regions or single genes can be determined to be responsible for specific features and malformations.

European Cytogeneticists Association Register of Unbalanced Chromosome Aberrations (ECARUCA); an online database for rare chromosome abnormalities.

During recent years a considerable improvement in diagnostic techniques has enabled cytogeneticists to find more and smaller chromosomal aberrations. However, accurate clinical knowledge about rare chromosome disorders is frequently lacking, mostly due to a significant decline in publishable cases. On the other hand, there is an increasing demand from parents and physicians for reliable information. In order to improve the quality and the quantity of data available, we designed a new database named the European Cytogeneticists Association Register of Unbalanced Chromosome Aberrations (ECARUCA) at http://www.ecaruca.net. This Internet-database contains cytogenetic and clinical data of patients with rare chromosome abnormalities, including microscopically visible aberrations, as well as microdeletions and -duplications. Cases with certain breakpoints collected in the Zurich Cytogenetic Database were transferred to ECARUCA. The advantages of ECARUCA compared to existing sources are that ECARUCA is interactive, dynamic and has long-term possibilities to store cytogenetic, molecular and clinical data. Professionals can login to submit new cases and perform searches in the database through the Internet. Currently the database contains 1500 unique chromosomal aberrations from almost 4000 patients. A frequent submission of new data ensures the up-to-date quality of the collection. Individual parent accounts allow parents to inform the ECARUCA team about the follow-up of their child. The ECARUCA database provides health care workers with accurate information on clinical aspects of rare chromosome disorders. Additionally, detailed correlations between chromosome aberrations and their phenotypes are of invaluable help in localising genes for mental retardation and congenital anomalies.

Neuroimaging in nine patients with inversion duplication of the short arm of chromosome 8.

Inversion duplication 8p is a rare chromosome disorder characterised by severe mental retardation, minor facial dysmorphisms, and corpus callosum agenesis. Few cerebral imaging studies have been reported. We describe 9 patients with an inversion duplication 8p, involving variable segments of the short arm of chromosome 8. MRI was performed in 8 patients and 2 patients underwent CT scanning. The images were systematically reviewed. All patients suffered from severe mental retardation. Head circumference was between 0 and + 2 SD in 7 patients. The corpus callosum was absent in 6, and thin (but complete) in 3 patients. Hypoplasia of the (inferior) cerebellar vermis was observed in 6 patients. Enlargement of the ventricular system and associated hippocampal maldevelopment were found in all patients. The supratentorial external CSF spaces were enlarged in 6 patients, and in 3 patients there was a remarkable enlargement of the retrocerebellar arachnoidal space. Cerebral white matter showed mildly delayed myelination in 7 patients, and periventricular lesions of variable extent in 6 patients. The pattern of imaging abnormalities was non-specific, but remarkably similar between patients. We found no correlation between the severity of the clinical features, imaging results, and extent of the chromosomal aberration.

Cryptic duplication of the distal segment of 22q due to a translocation (21;22): three case reports and a review of the literature.

Duplications of the proximal segment of chromosome 22q are not uncommon, like Cat-eye syndrome and duplications due to familial (11;22) translocations. However, duplications of the distal long arm of chromosome 22 (22qter) seem to be exceedingly rare. So far, duplications of 22q12 or 22q13 to 22qter have been described in 21 patients, of whom 13 had a pure duplication 22qter. Here we report on three new cases with a pure duplication of the distal part of 22q. The first patient carries a duplication of terminal 22q due to a de novo unbalanced translocation, 46,XX,der(21)t(21;22) (p13;q13.2), detected by NOR-staining, while the other patients have a familial cryptic duplication of terminal 22q due to an unbalanced translocation, 46,XY,der(21)t(21;22)(p10;q13.3). The last two patients were initially thought to have a polymorphic variant of 21p, but additional subtelomeric screening using FISH showed the extra material was derived from chromosome 22. Terminal duplications of 22qter may be more common than generally assumed, but due to its small size, especially when located on an acrocentric chromosome and/or possibly relatively mild phenotype remain undetected thus far.