Characteristics of genetic diseases in consanguineous populations in the genomic era: Lessons from Arab communities in North Israel.

The health outcome of consanguineous/endogamous unions is an increased risk of autosomal recessive disorders in their progeny. This manuscript is focused on consanguineous/endogamous populations living in North Israel. Molecular tools show that spouses' relatedness and hence their risks for congenital diseases among offspring are often greater than the risk calculated on the basis of reported pedigrees. Revealing founder mutations allow for effective genetic counseling, but also induce genetic screening of the whole community in case the mutations are found to be frequent. More complex genetic mechanisms, such as co-inheritance of more than one condition, allelic and even locus heterogeneity, have been identified. These mechanisms make genetic counseling more challenging but with the advancement of molecular techniques, diseases can be better deciphered. Yet, the presence of multiple mutations responsible for genetic diseases in isolated populations, and occasionally locus heterogeneity of diseases, is an unexpected phenomenon that still needs mechanistic clarification. It seems probably that addressing genetic counseling challenges and estimations of risks for genetic morbidity in consanguineous/endogamous couples will be achieved by introducing high-throughput genetic technologies into daily practice. The genomic era has expanded dramatically the translation of research products to genetic counseling tools, and this tendency is expected to yield a stronger impact in a near future.

Expanding the genotypic spectrum of Perrault syndrome.

Perrault syndrome is a rare autosomal recessive disorder characterized by sensorineural hearing loss (SNHL) in both sexes and primary ovarian insufficiency in 46, XX karyotype females. Biallelic variants in five genes are reported to be causative: HSD17B4, HARS2, LARS2, CLPP and C10orf2. Here we present eight families affected by Perrault syndrome. In five families we identified novel or previously reported variants in HSD17B4, LARS2, CLPP and C10orf2. The proband from each family was whole exome sequenced and variants confirmed by Sanger sequencing. A female was compound heterozygous for a known, p.(Gly16Ser) and novel, p.(Val82Phe) variant in D-bifunctional protein (HSD17B4). A family was homozygous for mitochondrial leucyl aminocyl tRNA synthetase (mtLeuRS) (LARS2) p.(Thr522Asn), previously associated with Perrault syndrome. A further family was compound heterozygous for mtLeuRS, p.(Thr522Asn) and a novel variant, p.(Met117Ile). Affected individuals with LARS2 variants had low frequency SNHL, a feature previously described in Perrault syndrome. A female with significant neurological disability was compound heterozygous for p.(Arg323Gln) and p.(Asn399Ser) variants in Twinkle (C10orf2). A male was homozygous for a novel variant in CLPP, p.(Cys144Arg). In three families there were no putative pathogenic variants in these genes confirming additional disease-causing genes remain unidentified. We have expanded the spectrum of disease-causing variants associated with Perrault syndrome.

Dysmorphology services: a snapshot of current practices and a vision for the future.

Dysmorphology concerns the recognition and management of rare, multiple anomaly syndromes. Genomic technologies and software for gestalt recognition will re-shape dysmorphology services. In order to reflect on a model of the service in the post-genomic era, we compared the utility of dysmorphology consultations in two Mediterranean cities, Athens, Greece and Afula, Israel (MDS), the Manchester Centre for Genomic Medicine, a UK service with dysmorphology expertise (UKDS) and the DYSCERNE, digital service (DDS). We show that it is more likely that chromosome microarray analysis will be performed if suggested in the UKDS rather than in the MDS; this, most probably reflects the difference of access to genetic testing following funding limitations in the MDS. We also show that in terms of achieved diagnosis, the first visit to a dysmorphology clinic is more significant than a follow-up. We show that a confirmed syndrome diagnosis significantly decreases the requests for other, non-genetic, laboratory investigations. Conversely, it increases the requests for reviews by other specialists and, most significantly (t-test: 8.244), it increases further requests for screening for possible associated complications. This is the first demonstration of the demands, on a health service, following the diagnosis of a dysmorphic condition.

A non-sense MCM9 mutation in a familial case of primary ovarian insufficiency.

Primary ovarian insufficiency (POI) results in an early loss of ovarian function, and remains idiopathic in about 80% of cases. Here, we have performed a complete genetic study of a consanguineous family with two POI cases. Linkage analysis and homozygosity mapping identified 12 homozygous regions with linkage, totalling 84 Mb. Whole-exome sequencing of the two patients and a non-affected sister allowed us to detect a homozygous causal variant in the MCM9 gene. The variant c.1483G>T [p.E495*], confirmed using Sanger sequencing, introduced a premature stop codon in coding exon 8 and is expected to lead to the loss of a functional protein. MCM9 belongs to a complex required for DNA repair by homologous recombination, and its impairment in mouse is known to induce meiotic recombination defects and oocyte degeneration. A previous study recently described two consanguineous families in which homozygous mutations of MCM9 were responsible for POI and short stature. Interestingly, the affected sisters in the family described here had a normal height. Altogether, our results provide the confirmation of the implication of MCM9 variants in POI and expand their phenotypic spectrum.

DMRTA2 (DMRT5) is mutated in a novel cortical brain malformation.

Lissencephaly is a phenotypically and genetically heterogeneous group of cortical brain malformations due to abnormal neuronal migration. The identification of many causative genes has increased the understanding of normal brain development. A consanguineous family was ascertained with three siblings affected by a severe prenatal neurodevelopmental disorder characterised by fronto-parietal pachygyria, agenesis of the corpus callosum and progressive severe microcephaly. Autozygosity mapping and exome sequencing identified a homozygous novel single base pair deletion, c.1197delT in DMRTA2, predicted to result in a frameshift variant p.(Pro400Leufs*33). DMRTA2 encodes doublesex and mab-3-related transcription factor a2, a transcription factor key to the development of the dorsal telencephalon. Data from murine and zebrafish knockout models are consistent with the variant of DMTRA2 (DMRT5) as responsible for the cortical brain phenotype. Our study suggests that loss of function of DMRTA2 leads to a novel disorder of cortical development.

Darier disease in Israel: combined evaluation of genetic and neuropsychiatric aspects.

BACKGROUND: Darier disease (DD) is a rare genodermatosis caused by heterozygous mutations in the ATP2A2 gene. It has been associated with neuropsychiatric manifestations. OBJECTIVES: To investigate the genetic basis of Israeli patients with DD, and its association with the neuropsychiatric phenotype. METHODS: A cohort of 32 families comprising 74 affected individuals and 13 unaffected family members was recruited from the Haemek Dermatology Department and other dermatology clinics in Israel. The individuals were evaluated by detailed questionnaires, physical examination and genetic analysis. The main outcome measures were genetic mutations, psychiatric profile and their association. RESULTS: Twenty-three mutations in ATP2A2 were scattered over the entire gene, 14 of them novel. Two families shared the same mutation. Twenty-one patients (28%) had a history of psychiatric disorders, most of them mood disorders. Another seven patients (9%) were highly suspected of having a psychiatric disorder; 21 (28%) reported suicidal thoughts and five (7%) had attempted suicide. The psychiatric phenotype demonstrated inter- and intrafamilial variability, and was not associated with disease severity, family history of psychiatric disease or mutation location. CONCLUSIONS: The cohort demonstrated genetic heterogeneity with no mutation cluster along the gene, and a high prevalence of psychiatric disorders. Although no clear genotype-phenotype correlation was found, the results point to a major effect of genetic background on psychiatric phenotype, together with other modifiers.

Learning disabilities in Darier's disease patients.

BACKGROUND: Neuropsychiatric features and intellectual difficulties have been reported in studies of Darier's disease. Learning disabilities have never been reported or evaluated systematically in these patients. OBJECTIVE: To assess the prevalence of learning disabilities in 76 patients with Darier's disease, and cognitive functioning in 19 of them. METHODS: The data were collected by two methods: a questionnaire, as part of a larger study on the clinical characteristics of 76 patients; and neuropsychological measures for the assessment of learning disabilities in 19 of them. RESULTS: Thirty-one of the 76 patients reported learning disabilities (41%) and 56 (74%) reported a family history of learning disabilities. Significant differences were found between the 19 patients evaluated on cognitive tasks and a control group of 42 skilled learners on subtraction and multiplication tasks. Six (32%) of the 19 were identified as having reading difficulties and five (26%) exhibited low performance on the Concentration Performance Test. All patients had general cognitive ability in the average range. CONCLUSIONS: Findings suggest an association between Darier's disease and learning disabilities, a heretofore unreported association, pointing to the need to obtain personal and family history of such disabilities in order to refer cases of clinical concern for further study.

Health-related quality of life among Darier's disease patients.

BACKGROUND: Darier's disease (DD) is an autosomal dominant skin disorder characterized by persistent eruption of hyperkeratotic papules. The effect of DD on quality of life (QOL) has been assessed in only one study, which found no correlation between the Dermatology Life Quality Index (DLQI) score and clinical severity of the disease. The correlation between health-related quality of life (HRQL) and other diseases and patient characteristics has not been studied. OBJECTIVES: To examine the HRQL of patients with DD and to evaluate the association between HRQL scores and disease and patient characteristics. METHODS: A total of 74 DD patients completed three QOL questionnaires: DLQI, EQ-5D, and one specially designed for the study. The data reported in this study were collected as part of a larger study on the clinical characteristics of DD; the socio-demographic and clinical data were used in the statistical analysis of the current study. RESULTS: Mean DLQI was 5.41 ± 5.57 and the mean EQ-Visual Analogue Scale (VAS), was 70.84 ± 19.25. DLQI and EQ-VAS were significantly associated with skin area affected, disease severity, age at onset of DD and a seborrhoeic distribution pattern of DD. Stepwise linear regression showed skin area affected to be the most significant variable in the predication of DLQI (beta = 0.183; SE = 0.04; P < 0.001), and disease severity the most significant variable in the predication of EQ-VAS (beta = -9.15; SE = 3.21; P < 0.006). CONCLUSIONS: Darier's disease has a negative impact on HRQL of patients and the HRQL is associated with various disease characteristics, mainly skin area affected and clinical severity.

Bacteriological aspects of Darier's disease.

BACKGROUND: There are no established data on the prevalence of bacterial colonization of lesional skin, nares and perineum in Darier's disease (DD), or its contribution to the clinical manifestations of the disease. OBJECTIVE: To determine the prevalence of bacterial colonization of lesional skin and Staphylococcus aureus (S. aureus) in nares and perineum in 75 patients with DD, the association of these parameters with disease and patient characteristics, and the features of the bacterial skin infection in this group. METHODS: Medical interviews and physical examinations were performed. Bacteria were isolated from swabs taken from lesional skin, nares and perineum. RESULTS: S. aureus was isolated in 68%, 47% and 22% of lesional skin, nares and perineum cultures respectively. Subjects with positive S. aureus culture from lesional skin and/or nares had a statistically significant higher percentage of skin area affected and a more severe disease than patients with negative culture. Thirty of the 75 patients (40%) recalled bacterial skin infection, most often on the chest. CONCLUSIONS: Patients with DD have high prevalence of S. aureus colonization in lesional skin and nares, with a correlation between disease severity and extent of the colonization. Further studies examining the consequences of S. aureus eradication in those sites may establish the need for S. aureus lesional skin and nares colonization screening and eradication as part of the treatment of DD exacerbations.

Hypotrichosis with juvenile macular dystrophy is caused by a mutation in CDH3, encoding P-cadherin.

Congenital hypotrichosis associated with juvenile macular dystrophy (HJMD; MIM601553) is an autosomal recessive disorder of unknown etiology, characterized by hair loss heralding progressive macular degeneration and early blindness. We used homozygosity mapping in four consanguineous families to localize the gene defective in HJMD to 16q22.1. This region contains CDH3, encoding P-cadherin, which is expressed in the retinal pigment epithelium and hair follicles. Mutation analysis shows in all families a common homozygous deletion in exon 8 of CDH3. These results establish the molecular etiology of HJMD and implicate for the first time a cadherin molecule in the pathogenesis of a human hair and retinal disorder.

A randomized trial to investigate needle redirections/re-insertions using a handheld ultrasound device versus traditional palpation for spinal anesthesia in obese women undergoing cesarean delivery.

BACKGROUND: Ultrasound may be useful to identify the spinal anesthesia insertion point, particularly when landmarks are not palpable. We tested the hypothesis that the number of needle redirections/re-insertions is lower when using a handheld ultrasound device compared with palpation in obese women undergoing spinal anesthesia for cesarean delivery. METHODS: Study recruits were obese (body mass index (BMI) >30 kg/m2) women with impalpable bony landmarks who were undergoing spinal anesthesia for elective cesarean delivery. Women were randomized to ultrasound or palpation. The primary study outcome was a composite between-group comparison of total number of needle redirections (any withdrawal and re-advancement of the needle and/or introducer within the intervertebral space) or re-insertions (any new skin puncture in the same or different intervertebral space) per patient. Secondary outcomes included insertion site identification time and patient verbal numerical pain score (0-10) for comfort during surgical skin incision. RESULTS: Forty women completed the study. The mean BMI (standard deviation) for the ultrasound group was 39.8 (5.5) kg/m2 and for the palpation group 37.3 (5.2) kg/m2. There was no difference in the composite primary outcome (median (interquartile range) [range]) between the ultrasound group (4 (2-13) [2-22]) and the palpation group (6 (4-10) [1-17]) (P=0.22), with the 95% confidence interval of the difference 2 (-1.7 to 5.7). There were no differences in the secondary outcomes. CONCLUSIONS: Handheld ultrasound did not demonstrate any advantages over traditional palpation techniques for spinal anesthesia in an obese population undergoing cesarean delivery, although the study was underpowered to show a difference.

Identification of a prevalent founder mutation in an Israeli Muslim Arab village confirms the role of PRCD in the aetiology of retinitis pigmentosa in humans.

BACKGROUND: Retinitis pigmentosa (RP) is the most common form of hereditary retinal degeneration. At least 32 genes and loci have been implicated in non-syndromic autosomal recessive RP. Progressive rod-cone degeneration is a canine form of autosomal recessive retinal degeneration, which serves as an animal model for human RP, and is caused by a missense mutation of the PRCD gene. The same homozygous PRCD mutation has been previously identified in a single human RP patient from Bangladesh. To date, this is the only RP-causing mutation of PRCD reported in humans. METHODS: The cause of the high incidence rate of autosomal recessive RP in an isolated Muslim Arab village in Northern Israel was investigated by haplotype analysis in affected families. The underlying mutation was detected by direct sequencing of the causative gene, and its prevalence in affected and unaffected individuals from the village was determined. Patients who were homozygotes for this mutation underwent ophthalmic evaluation, including funduscopy and electroretinography. RESULTS AND CONCLUSIONS: The identification of a novel pathogenic nonsense mutation of PRCD is reported. This founder mutation was found in a homozygous state in 18 patients from nine families, and its carrier frequency in the investigated village is 10%. The mutation is associated with a typical RP phenotype, including bone spicule-type pigment deposits and non-recordable electroretinograms. Additional findings include signs of macular degeneration and cataract. The identification of a second pathogenic mutation of PRCD in multiple RP patients confirms the role of PRCD in the aetiology of RP in humans.

Dependence of maternal serum [AFP]/[hCG] median ratios on age of gestation: comparison of trisomy 21 to euploid pregnancies.

BACKGROUND: Current risk calculations for trisomy 21, which are based on multiples of median (MoM), do not take into account possible differences between euploid and trisomy 21 pregnancies that may develop with gestational age. In order to optimize the predictive value of screening tests, we calculated the ratio between maternal serum concentration of alpha-fetoprotein (AFP) and that of human chorionic gonadotropin (hCG) in euploid and in trisomy 21 pregnancies. METHODS: The medians of the concentration ratios, [AFP]/[hCG] at 16-21 weeks of gestation, were plotted as a function of gestational age for 307 cases of trisomy 21 and were compared with the medians of 30 549 normal karyotype cases. RESULTS: [AFP]/[hCG] ratio medians were independent of body weight and maternal age. There was a significant difference in the [AFP]/[hCG] ratio when comparing trisomy 21 and euploid pregnancies at each week. This difference became greater with advancing gestational age (P < 0.01). CONCLUSION: There is a significant difference in ratios of [AFP]/[hCG] between euploid and trisomy 21 pregnancies, which may be used to improve detection rates of Down syndrome screening.

Severe infantile type of carnitine palmitoyltransferase II (CPT II) deficiency due to homozygous R503C mutation.

We report a patient with severe infantile carnitine palmitoyltransferase II (CPT II) deficiency who died at the age of 3 months. Genetic analysis of the CPT2 gene revealed that the patient was homozygous, and her parents were heterozygous, for a R503C missense mutation. Heterozygosity for R503C, without a second mutation, has previously been reported in symptomatic patients from two families, one with the mild adult myopathic form and one with malignant hyperthermia. In contrast, the R503C heterozygous parents of the patient were entirely asymptomatic, suggesting that additional genetic and/or environmental factors must have contributed to the occurrence of symptoms in previously reported carriers. Our findings indicate that the mutation R503C should be added to the handful of mutations associated with the severe phenotype when present in the homozygous state or combined with another severe mutation.