A novel SLC5A6 homozygous variant in a family with multivitamin-dependent neurometabolic disorder: Phenotype expansion and long-term follow-up.

The sodium-dependent multivitamin transporter (hSMVT) encoded by the SLC5A6 gene is required for the intestinal absorption of biotin, pantothenic acid and lipoate, three micronutrients essential for normal growth and development. Systemic deficiency of these elements, either occurring from nutritional causes or genetic defects, is associated with neurological disorders, growth delay, skin and hair changes, metabolic and immunological abnormalities. A few patients with biallelic variants of SLC5A6 have been reported, exhibiting a spectrum of neurological and systemic clinical features with variable severity. We describe three patients from a single family carrying a homozygous p.(Leu566Valfs*33) variant of SLC5A6 disrupting the frame of the C-terminal portion of the hSMVT. In these patients, we documented a severe disorder featuring developmental delay, sensory polyneuropathy, optic atrophy, recurrent infections, and repeated episodes of intestinal pseudo-obstruction. Two patients who did not receive multivitamin supplementation therapy died in early infancy. In a third patient, early supplementation of biotin and pantothenic acid stabilized the clinical picture changing the course of the disease. These findings extend genotype-phenotype correlations and show how a timely and lifelong multivitamin treatment may be crucial to reduce the risk of life-threatening events in patients with pathogenic variants of the SLC5A6 gene.

A young boy with ventricular arrhythmias and thyroid dysgenesis: two genes are not enough?

Abstract Congenital hypothyroidism (CH) may be caused by biallelic variants in the TSHR gene. CH due to thyroid dysgenesis has also been linked to pathogenic variants of the nucleotide kinase 2, homeobox 5 (NKX2-5) gene, which can also cause sudden cardiac death from ventricular arrhythmia. In particular, the NKX2-5 p.Arg25Cys missense variant has been repeatedly reported in patients with congenital heart defects and, more rarely, with hypogonadism. We report the case of a 7 year old boy with ventricular arrhythmias, thyroid dysgenesis and intellectual disability, born from consanguineous Tunisian parents. Exome sequencing and segregation analysis revealed two potentially relevant variants: the NKX2-5 p.Arg25Cys variant (maternally inherited), as well as a single heterozygous TSHR p.Gln90Pro variant (paternally inherited). Of note, a male sibling of the proband, presenting with intellectual disability only, carried the same two variants. No other TSHR variants, or other potentially relevant variants were identified. In this proband, despite the identification of variants in two genes potentially correlated to the phenotype, a definite genetic diagnosis could not be reached. This case report highlights the complexity of exome data interpretation, especially when dealing with families presenting complex phenotypes and variable expression of clinical traits.

A young boy with ventricular arrhythmias and thyroid dysgenesis: two genes are not enough?

Congenital hypothyroidism (CH) may be caused by biallelic variants in the TSHR gene. CH due to thyroid dysgenesis has also been linked to pathogenic variants of the nucleotide kinase 2, homeobox 5 (NKX2-5) gene, which can also cause sudden cardiac death from ventricular arrhythmia. In particular, the NKX2-5 p.Arg25Cys missense variant has been repeatedly reported in patients with congenital heart defects and, more rarely, with hypogonadism. We report the case of a 7 year old boy with ventricular arrhythmias, thyroid dysgenesis and intellectual disability, born from consanguineous Tunisian parents. Exome sequencing and segregation analysis revealed two potentially relevant variants: the NKX2-5 p.Arg25Cys variant (maternally inherited), as well as a single heterozygous TSHR p.Gln90Pro variant (paternally inherited). Of note, a male sibling of the proband, presenting with intellectual disability only, carried the same two variants. No other TSHR variants, or other potentially relevant variants were identified. In this proband, despite the identification of variants in two genes potentially correlated to the phenotype, a definite genetic diagnosis could not be reached. This case report highlights the complexity of exome data interpretation, especially when dealing with families presenting complex phenotypes and variable expression of clinical traits.

Further delineation and long-term evolution of electroclinical phenotype in Mowat Wilson Syndrome. A longitudinal study in 40 individuals.

BACKGROUND: Epilepsy is a main feature of Mowat Wilson Syndrome (MWS), a congenital malformation syndrome caused by ZEB2 variants. The aim of this study was to investigate the long-term evolution of the electroclinical phenotype of MWS in a large population. METHODS: Forty-individuals with a genetically confirmed diagnosis were enrolled. Three age groups were identified (t1 = 0-4; t2 = 5-12; t3 = >13 years); clinical data and EEG records were collected, analyzed, and compared for age group. Video-EEG recorded seizures were reviewed. RESULTS: Thirty-six of 40 individuals had epilepsy, of whom 35/35 aged >5 years. Almost all (35/36) presented focal seizures at onset (mean age at onset 3.4 ±â€¯2.3 SD) that persisted, reduced in frequency, in 7/22 individuals after the age of 13. Absences occurred in 22/36 (mean age at onset 7.2 ±â€¯0.9 SD); no one had absences before 6 and over 16 years old. Paroxysmal interictal abnormalities in sleep also followed an age-dependent evolution with a significant increase in frequency at school age (p = 0.002) and a reduction during adolescence (p = 0.008). Electrical Status Epilepticus during Sleep occurred in 14/36 (13/14 aged 5-13 years old at onset). Seven focal seizure ictal video-EEGs were collected: all were long-lasting and more visible clinical signs were often preceded by prolonged electrical and/or subtle (erratic head and eye orientation) seizures. Valproic acid was confirmed as the most widely used and effective drug, followed by levetiracetam. CONCLUSIONS: Epilepsy is a major sign of MWS with a characteristic, age-dependent, electroclinical pattern. Improvement with adolescence/adulthood is usually observed. Our data strengthen the hypothesis of a GABAergic transmission imbalance underlying ZEB2-related epilepsy.

Generalized Arterial Calcification of Infancy Type 1 (GACI1): Identification of a Novel Pathogenic Variant (c.1715T>C (p.Leu572Ser)).

Generalized Arterial Calcification of Infancy (GACI) is a rare disease inherited in a recessive manner, with severe and diffuse early onset of calcifications along the internal elastic lamina in large and medium size arteries. The diagnosis results are from clinical manifestations, imaging, histopathologic exams, and genetic tests. GACI is predominantly caused by biallelic pathogenic variant in the ENPP1 gene (GACI1, OMIM#208000) and, to a lesser extent, by pathogenic variants in the ABCC6 gene (GACI2, OMIM#614473). We present a novel variation in the ENPP1 gene identified in a patient clinically diagnosed with GACI and confirmed by genetic investigation and autopsy as GACI type 1. The sequence analysis of the patient's ENPP1 gene detected two heterozygous variants c.1412A>G (p.Tyr471Cys) and c.1715T>C (p.Leu572Ser). The variant c.1715T>C (p.Leu572Ser) has not been described yet in the literature and in mutation databases. A genetic analysis was also carried out for the parents of the newborn; the heterozygous pathogenic variant c.1412A>G (p.Tyr471Cys) was detected in the mother's ENPP1 gene, and a sequence analysis of the father's ENPP1 gene revealed the novel heterozygous variant c.1715T>C (p.Leu572Ser). Our results showed that the variant c.1715T>C (p.Leu572Ser) may have a pathogenic role in the development of GACI type1 (GACI1, OMIM#208000), at least when associated with the pathogenic c.1412A>G (p.Tyr471Cys) variant. The identification of novel mutations potentially enabled genotype/phenotype associations that will ultimately have an impact on clinical management and prognosis for the disease.

ANO10 mutational screening in recessive ataxia: genetic findings and refinement of the clinical phenotype.

Autosomal recessive cerebellar ataxia type 3 (ARCA3) is a rare inherited disorder caused by mutations in the ANO10 gene. The disease is characterized by slowly progressive spastic ataxia variably associated with motor neuron involvement, epilepsy, and cognitive decline. We performed mutational screening in 80 patients with sporadic or autosomal recessive adult-onset ataxia. We identified 11 ANO10 gene variants in 10 patients from 8 families (10%): 4 mutations were previously described and 7 were novel. Age at onset ranged between 27 and 53 years. All patients presented ataxia, pyramidal signs and cerebellar atrophy at brain MRI. Additional signs were bradykinesia (7/10), mild vertical gaze paresis (5/10), pes cavus (4/10), and sphincteric disturbances (3/10). Six patients, with normal MMSE score, failed several neuropsychological tests rating executive functions. Three patients had giant somatosensory evoked potentials and epileptic spikes in EEG without clinical evidence of seizures. Our observational study indicates a high frequency of ARCA3 disease in sporadic patients with adult-onset cerebellar ataxia. We extended the ANO10 mutational spectrum with the identification of novel gene variants, and further defined the clinical, cognitive, and neurophysiological features in a new cohort of patients. These findings may contribute to the refinement of the complex ARCA3 phenotype and be valuable in clinical management and natural history studies.

The genetic and clinical spectrum of a large cohort of patients with distal renal tubular acidosis.

Primary distal renal tubular acidosis is a rare genetic disease. Mutations in SLC4A1, ATP6V0A4, and ATP6V1B1 genes have been described as the cause of the disease, transmitted as either an autosomal dominant or recessive trait. Particular clinical features, such as sensorineural hearing loss, have been mainly described in association with mutations in one gene instead of the others. Nevertheless, the diagnosis of distal renal tubular acidosis is essentially based on clinical and laboratory findings, and the series of patients described so far are usually represented by small cohorts. Therefore, a strict genotype-phenotype correlation is still lacking, and questions about whether clinical and laboratory data should direct the genetic analysis remain open. Here, we applied next-generation sequencing in 89 patients with a clinical diagnosis of distal renal tubular acidosis, analyzing the prevalence of genetic defects in SLC4A1, ATP6V0A4, and ATP6V1B1 genes and the clinical phenotype. A genetic cause was determined in 71.9% of cases. In our group of sporadic cases, clinical features, including sensorineural hearing loss, are not specific indicators of the causal underlying gene. Mutations in the ATP6V0A4 gene are quite as frequent as mutations in ATP6V1B1 in patients with recessive disease. Chronic kidney disease was frequent in patients with a long history of the disease. Thus, our results suggest that when distal renal tubular acidosis is suspected, complete genetic testing could be considered, irrespective of the clinical phenotype of the patient.

Neuroimaging findings in Mowat-Wilson syndrome: a study of 54 patients.

PURPOSE: Mowat-Wilson syndrome (MWS) is a genetic disease characterized by distinctive facial features, moderate to severe intellectual disability, and congenital malformations, including Hirschsprung disease, genital and eye anomalies, and congenital heart defects, caused by haploinsufficiency of the ZEB2 gene. To date, no characteristic pattern of brain dysmorphology in MWS has been defined. METHODS: Through brain magnetic resonance imaging (MRI) analysis, we delineated a neuroimaging phenotype in 54 MWS patients with a proven ZEB2 defect, compared it with the features identified in a thorough review of published cases, and evaluated genotype-phenotype correlations. RESULTS: Ninety-six percent of patients had abnormal MRI results. The most common features were anomalies of corpus callosum (79.6% of cases), hippocampal abnormalities (77.8%), enlargement of cerebral ventricles (68.5%), and white matter abnormalities (reduction of thickness 40.7%, localized signal alterations 22.2%). Other consistent findings were large basal ganglia, cortical, and cerebellar malformations. Most features were underrepresented in the literature. We also found ZEB2 variations leading to synthesis of a defective protein to be favorable for psychomotor development and some epilepsy features but also associated with corpus callosum agenesis. CONCLUSION: This study delineated the spectrum of brain anomalies in MWS and provided new insights into the role of ZEB2 in neurodevelopment.Genet Med advance online publication 10 November 2016.

Syndromic intellectual disability: a new phenotype caused by an aromatic amino acid decarboxylase gene (DDC) variant.

The causative variant in a consanguineous family in which the three patients (two siblings and a cousin) presented with intellectual disability, Marfanoid habitus, craniofacial dysmorphisms, chronic diarrhea and progressive kyphoscoliosis, has been identified through whole exome sequencing (WES) analysis. WES study identified a homozygous DDC variant in the patients, c.1123C>T, resulting in p.Arg375Cys missense substitution. Mutations in DDC cause a recessive metabolic disorder (aromatic amino acid decarboxylase, AADC, deficiency, OMIM #608643) characterized by hypotonia, oculogyric crises, excessive sweating, temperature instability, dystonia, severe neurologic dysfunction in infancy, and specific abnormalities of neurotransmitters and their metabolites in the cerebrospinal fluid (CSF). In our family, analysis of neurotransmitters and their metabolites in patient's CSF shows a pattern compatible with AADC deficiency, although the clinical signs are different from the classic form. Our work expands the phenotypic spectrum associated with DDC variants, which therefore can cause an additional novel syndrome without typical movement abnormalities.

Mutational screening of NOTCH3 gene reveals two novel mutations: complexity of CADASIL diagnosis.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an adult onset hereditary vascular disease with neurological manifestations. The classical clinical course is relentlessly progressive with early transient ischaemic attacks (TIA) or strokes, dementia and finally death in the mid-1960s. The disorder is inherited in an autosomal dominant fashion, with high penetrance and broad variable clinical course even within family. It is caused by mutations in the NOTCH3 gene; all causative mutations result in gain or loss of a cysteine residue within the extracellular domain, with exons 3 and 4 reported as hot spot mutational sites. Mutation analysis of the NOTCH3 gene was performed through direct sequencing of the 2-23 exons containing all EGF-like domains. Patients underwent genetic counselling pre and post testing. Here, we report two novel mutations located in exons 6 and 15 of the NOTCH3 gene; clinical description for the probands and for available relatives is enclosed. No reliable data on incidence or prevalence rates of this disease are available: it is therefore essential that the diagnosis is obtained in all suspected cases through the extensive analysis of the NOTCH3 gene and that all cases are brought to the attention of the scientific community.

Epilepsy in Mowat-Wilson syndrome: delineation of the electroclinical phenotype.

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene and is characterized by distinctive facial features, epilepsy, moderate to severe intellectual disability, corpus callosum abnormalities and other congenital malformations. Epilepsy is considered a main manifestation of the syndrome, with a prevalence of about 70-75%. In order to delineate the electroclinical phenotype of epilepsy in MWS, we investigated epilepsy onset and evolution, including seizure types, EEG features, and response to anti-epileptic therapies in 22 patients with genetically confirmed MWS. Onset of seizures occurred at a median age of 14.5 months (range: 1-108 months). The main seizure types were focal and atypical absence seizures. In all patients the first seizure was a focal seizure, often precipitated by fever. The semiology was variable, including hypomotor, versive, or focal clonic manifestations; frequency ranged from daily to sporadic. Focal seizures were more frequent during drowsiness and sleep. In 13 patients, atypical absence seizures appeared later in the course of the disease, usually after the age of 4 years. Epilepsy was usually quite difficult to treat: seizure freedom was achieved in nine out of the 20 treated patients. At epilepsy onset, the EEGs were normal or showed only mild slowing of background activity. During follow-up, irregular, diffuse frontally dominant and occasionally asymmetric spike and waves discharges were seen in most patients. Sleep markedly activated these abnormalities, resulting in continuous or near-to-continuous spike and wave activity during slow wave sleep. Slowing of background activity and poverty of physiological sleep features were seen in most patients. Our data suggest that a distinct electroclinical phenotype, characterized by focal and atypical absence seizures, often preceded by febrile seizures, and age-dependent EEG changes, can be recognized in most patients with MWS.

De novo unbalanced translocations in Prader-Willi and Angelman syndrome might be the reciprocal product of inv dup(15)s.

The 15q11-q13 region is characterized by high instability, caused by the presence of several paralogous segmental duplications. Although most mechanisms dealing with cryptic deletions and amplifications have been at least partly characterized, little is known about the rare translocations involving this region. We characterized at the molecular level five unbalanced translocations, including a jumping one, having most of 15q transposed to the end of another chromosome, whereas the der(15)(pter->q11-q13) was missing. Imbalances were associated either with Prader-Willi or Angelman syndrome. Array-CGH demonstrated the absence of any copy number changes in the recipient chromosome in three cases, while one carried a cryptic terminal deletion and another a large terminal deletion, already diagnosed by classical cytogenetics. We cloned the breakpoint junctions in two cases, whereas cloning was impaired by complex regional genomic architecture and mosaicism in the others. Our results strongly indicate that some of our translocations originated through a prezygotic/postzygotic two-hit mechanism starting with the formation of an acentric 15qter->q1::q1->qter representing the reciprocal product of the inv dup(15) supernumerary marker chromosome. An embryo with such an acentric chromosome plus a normal chromosome 15 inherited from the other parent could survive only if partial trisomy 15 rescue would occur through elimination of part of the acentric chromosome, stabilization of the remaining portion with telomere capture, and formation of a derivative chromosome. All these events likely do not happen concurrently in a single cell but are rather the result of successive stabilization attempts occurring in different cells of which only the fittest will finally survive. Accordingly, jumping translocations might represent successful rescue attempts in different cells rather than transfer of the same 15q portion to different chromosomes. We also hypothesize that neocentromerization of the original acentric chromosome during early embryogenesis may be required to avoid its loss before cell survival is finally assured.

Familial Poland anomaly revisited.

Poland anomaly (PA) is a pectoral muscle hypoplasia/aplasia variably associated with ipsilateral thoracic (TA) and/or upper limb anomalies (ULA). PA is usually sporadic and sometimes familial, making recurrence risk an issue in genetic counseling. Multidisciplinary evaluation of 240 PA patients was carried out, including physical examination of patients and their parents in 190 PA (subjects of the study). Familial conditions were classified into three groups. Group1: true familial PA (F-PA): pectoral muscle defects with familial recurrence: 8(4.2%). Group2: familial Poland-like anomaly families (F-PLA): PA index case and ≥1 relative(s) showing normal pectoral muscles but ULA and/or TA common in PA: 16(8.4%). Group3: sporadic PA (S-PA): 166(87.4%). F-PA indicated a stronger male (87.5%) and left side (62.5%) prevalence, but fewer ULA (37.5%) compared to the other two groups. Maternal transmission (6/8) was more common in F-PA. Statistical significance was not reached due to the small number of F-PA and F-PLA. Karyotyping and array-comparative genomic hybridization were performed in 13 families. Three maternally inherited copy number variants were identified in three patients: 1p31.1 deletion, Xp11.22 duplication, and 16q23.1 duplication. Interestingly, the proband's mother carrying the 16q23.1 duplication displayed moderate breast and areola asymmetry, but normal pectoral muscles on ultrasound. Though there is no recent review discussing recurrence of PA, we reviewed 31 published PA families. On the basis of our study and previous reports, familial PA is not uncommon. Nonetheless, no information can be derived either regarding a molecular basis or clinical tools with which to identify cases with recurrence risk.

Risk of congenital anomalies around a municipal solid waste incinerator: a GIS-based case-control study.

BACKGROUND: Waste incineration releases into the environment toxic substances having a teratogenic potential, but little epidemiologic evidence is available on this topic. We aimed at examining the relation between exposure to the emissions from a municipal solid waste incinerator and risk of birth defects in a northern Italy community, using Geographical Information System (GIS) data to estimate exposure and a population-based case-control study design. By modelling the incinerator emissions, we defined in the GIS three areas of increasing exposure according to predicted dioxins concentrations. We mapped the 228 births and induced abortions with diagnosis of congenital anomalies observed during the 1998-2006 period, together with a corresponding series of control births matched for year and hospital of birth/abortion as well as maternal age, using maternal address in the first three months of pregnancy to geocode cases and controls. RESULTS: Among women residing in the areas with medium and high exposure, prevalence of anomalies in the offspring was substantially comparable to that observed in the control population, nor dose-response relations for any of the major categories of birth defects emerged. Furthermore, odds ratio for congenital anomalies did not decrease during a prolonged shut-down period of the plant. CONCLUSION: Overall, these findings do not lend support to the hypothesis that the environmental contamination occurring around an incineration plant such as that examined in this study may induce major teratogenic effects.

Adverse pregnancy outcomes in a population exposed to the emissions of a municipal waste incinerator.

Some contaminants emitted by municipal waste incinerators are believed to adversely affect reproductive health in the exposed populations; yet only limited and conflicting epidemiologic evidence on this issue has been provided so far. In this study we analyzed rates of spontaneous abortion and prevalence at birth of congenital anomalies in women residing or working near the municipal solid waste incinerator of Modena, northern Italy, during the 2003--2006 period and who experienced higher levels of exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans, compared to the remaining municipal population. In women residing in two areas close to the incinerator plant with increasing exposure to dioxins, we did not detect an excess risk of miscarriage (relative risk [RR] 1.00, 95% confidence interval [CI] 0.65-1.48) and of birth defects (RR 0.64, 95% CI 0.20-1.55), nor did any indication of dose-response relation emerge. Among female workers employed in the factories located in the exposed areas, we did not observe a higher risk of spontaneous abortion (RR 1.04, 95% CI 0.38-2.30); however, an increase in prevalence of birth defects was noted (RR 2.26), although this risk estimate was statistically very unstable (95% CI 0.57-6.14). Overall, the study results provide little evidence of an excess risk of adverse pregnancy outcomes in women exposed to emissions from a modern municipal solid waste incinerator.

Associated anomalies in multi-malformed infants with cleft lip and palate: An epidemiologic study of nearly 6 million births in 23 EUROCAT registries.

We studied 5,449 cases of cleft lip (CL) with or without cleft palate (CL/P) identified between 1980 and 2000 from the EUROCAT network of 23 registers (nearly 6 million births) in 14 European countries. We investigated specific types of defects associated with clefts. Among CL/P cases (prevalence = 9.1 per 10,000), 1,996 (36.6%) affected only the lip (CL) and 3,453 (63.4%) involved CL and palate (CLP). A total of 3,860 CL/P cases (70.8%) occurred as isolated anomalies and 1,589 (29.2%) were associated with other defects such as multiple congenital anomalies of unknown origin (970), chromosomal (455) and recognized syndromes (164). Associated malformations were more frequent in infants who had CLP (34.0%) than in infants with CL only (20.8%). Among multi-malformed infants, 2 unrelated anomalies were found in 351 cases, 3 in 242 cases, and 4 or more in 377 cases. Among 5,449 CL/P cases, 4,719 were live births (LB) (86.6%), 203 stillbirths (SB) (3.7%), while 508 (9.3%) were terminations of pregnancy (ToP). CL/P occurred significantly more frequently in males (M/F = 1.70), especially among total isolated cases (M/F = 1.87) and CLP isolated cases (M/F = 1.92). The study confirmed that musculoskeletal, cardiovascular, and central nervous system defects are frequently associated with CL/P. An association with reduction anomalies of the brain was found. This association suggests that clinicians should seek to identify structural brain anomalies in these patients with CL/P as the potential functional consequences may be important for rehabilitation and clinical management.

FISH screening for subtelomeric rearrangements in 219 patients with idiopathic mental retardation and normal karyotype.

Subtelomeric rearrangements are a common cause of idiopathic mental retardation (MR) accounting for 6.3-10.2% of moderate to severe cases and less than 1% of mildly retarded patients. We report on a cohort of 219 patients with idiopathic MR and normal 400-550 band karyotype screened for subtelomeric rearrangements by multiprobe Fluorescence in situ hybridization (FISH) in three Italian Genetics Centers. Twelve positive cases (5.5%) were found. Six were de novo deletions (1p, 7p, 9p, 9q, 20p, 22q) and four unbalanced translocations [a der(6)t(6q; 18p) and a der(18)t(8p; 18q) both de novo, a der(12)t(12p; 17q)mat and a der(2)t(2q; 17q) of unknown origin]. The remaining two cases were apparently balanced reciprocal translocations [a t(4p; 18q) and a t(1p; 16p)] of undetermined origin whose role in the pathogenesis of the clinical phenotype is doubtful. Dysmorphic features were present in all unbalanced patients, whilst a family history of MR was present in only four of them. The proposition that subtelomeric rearrangements are a significant cause of idiopathic MR is supported by our survey. Collection of the clinical data of positive patients will help to delineate the phenotype associated with the various subtelomeric abnormalities, to tailor healthcare services to the needs of these patients and their families and to determine the appropriate use of the test.