Early neurological signs in infants identified through neonatal screening for SMA: do they predict outcome?

Neonatal screening for SMA has allowed the identification of infants who may present with early clinical signs. Our aim was to establish whether the presence and the severity of early clinical signs have an effect on the development of motor milestones. Infants identified through newborn screening were prospectively assessed using a structured neonatal neurological examination and an additional module developed for the assessment of floppy infants. As part of the follow-up, all infants were assessed using the HINE-2 to establish developmental milestones. Only infants with at least 24 months of follow-up were included. Normal early neurological examination (n = 11) was associated with independent walking before the age of 18 months while infants with early clinical signs of SMA (n = 4) did not achieve ambulation (duration follow-up 33.2 months). Paucisymptomatic patients (n = 3) achieved ambulation, one before the age of 18 months and the other 2 between 22 and 24 months.  Conclusion: Our findings suggest that early clinical signs may contribute to predict motor milestones development. What is Known: • There is increasing evidence of heterogeneity among the SMA newborns identified via NBS. • The proposed nosology describes a clinically silent disease, an intermediate category ('paucisymptomatic') and 'symptomatic SMA'. What is New: • The presence of minimal clinical signs at birth does not prevent the possibility to achieve independent walking but this may occur with some delay. • The combination of genotype at SMN locus and clinical evaluation may better predict the possibility to achieve milestones.

Two more families supporting the existence of monogenic spinocerebellar ataxia 48.

The reduced penetrance of TBP intermediate alleles and the recently proposed possible digenic TBP/STUB1 inheritance raised questions on the possible mechanism involved opening a debate on the existence of SCA48 as a monogenic disorder. We here report clinical and genetic results of two apparently unrelated patients carrying the same STUB1 variant(c.244G > T;p.Asp82Tyr) with normal TBP alleles and a clinical picture fully resembling SCA48, including cerebellar ataxia, dysarthria and mild cognitive impairment. This report provides supportive evidence that this specific ataxia can also occur as a monogenic disease, considering classical TBP allelic ranges.

Genomic analysis of 116 autism families strengthens known risk genes and highlights promising candidates.

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a strong genetic component in which rare variants contribute significantly to risk. We performed whole genome and/or exome sequencing (WGS and WES) and SNP-array analysis to identify both rare sequence and copy number variants (SNVs and CNVs) in 435 individuals from 116 ASD families. We identified 37 rare potentially damaging de novo SNVs (pdSNVs) in the cases (n = 144). Interestingly, two of them (one stop-gain and one missense variant) occurred in the same gene, BRSK2. Moreover, the identification of 8 severe de novo pdSNVs in genes not previously implicated in ASD (AGPAT3, IRX5, MGAT5B, RAB8B, RAP1A, RASAL2, SLC9A1, YME1L1) highlighted promising candidates. Potentially damaging CNVs (pdCNVs) provided support to the involvement of inherited variants in PHF3, NEGR1, TIAM1 and HOMER1 in neurodevelopmental disorders (NDD), although mostly acting as susceptibility factors with incomplete penetrance. Interpretation of identified pdSNVs/pdCNVs according to the ACMG guidelines led to a molecular diagnosis in 19/144 cases, although this figure represents a lower limit and is expected to increase thanks to further clarification of the role of likely pathogenic variants in ASD/NDD candidate genes not yet established. In conclusion, our study highlights promising ASD candidate genes and contributes to characterize the allelic diversity, mode of inheritance and phenotypic impact of de novo and inherited risk variants in ASD/NDD genes.

Structural brain abnormalities in Pallister-Killian syndrome: a neuroimaging study of 31 children.

BACKGROUND: Pallister-Killian syndrome (PKS) is a rare genetic disorder caused by mosaic tetrasomy of 12p with wide neurological involvement. Intellectual disability, developmental delay, behavioral problems, epilepsy, sleep disturbances, and brain malformations have been described in most individuals, with a broad phenotypic spectrum. This observational study, conducted through brain MRI scan analysis on a cohort of patients with genetically confirmed PKS, aims to systematically investigate the neuroradiological features of this syndrome and identify the possible existence of a typical pattern. Moreover, a literature review differentiating the different types of neuroimaging data was conducted for comparison with our population. RESULTS: Thirty-one individuals were enrolled (17 females/14 males; age range 0.1-17.5 years old at first MRI). An experienced pediatric neuroradiologist reviewed brain MRIs, blindly to clinical data. Brain abnormalities were observed in all but one individual (compared to the 34% frequency found in the literature review). Corpus callosum abnormalities were found in 20/30 (67%) patients: 6 had callosal hypoplasia; 8 had global hypoplasia with hypoplastic splenium; 4 had only hypoplastic splenium; and 2 had a thin corpus callosum. Cerebral hypoplasia/atrophy was found in 23/31 (74%) and ventriculomegaly in 20/31 (65%). Other frequent features were the enlargement of the cisterna magna in 15/30 (50%) and polymicrogyria in 14/29 (48%). Conversely, the frequency of the latter was found to be 4% from the literature review. Notably, in our population, polymicrogyria was in the perisylvian area in all 14 cases, and it was bilateral in 10/14. CONCLUSIONS: Brain abnormalities are very common in PKS and occur much more frequently than previously reported. Bilateral perisylvian polymicrogyria was a main aspect of our population. Our findings provide an additional tool for early diagnosis.Further studies to investigate the possible correlations with both genotype and phenotype may help to define the etiopathogenesis of the neurologic phenotype of this syndrome.

Whole genome analysis of rare deleterious variants adds further evidence to BRSK2 and other risk genes in Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a strong genetic component in which rare variants contribute significantly to risk. We have performed whole genome and/or exome sequencing (WGS and WES) and SNP-array analysis to identify both rare sequence and copy number variants (SNVs and CNVs) in 435 individuals from 116 ASD families. We identified 37 rare potentially damaging de novo SNVs (pdSNVs) in cases (n = 144). Interestingly, two of them (one stop-gain and one missense variant) occurred in the same gene, BRSK2. Moreover, the identification of 9 severe de novo pdSNVs in genes not previously implicated in ASD (RASAL2, RAP1A, IRX5, SLC9A1, AGPAT3, MGAT3, RAB8B, MGAT5B, YME1L1), highlighted novel candidates. Potentially damaging CNVs (pdCNVs) provided support to the involvement of inherited variants in PHF3, NEGR1, TIAM1 and HOMER1 in neurodevelopmental disorders (NDD), although mostly acting as susceptibility factors with incomplete penetrance. Interpretation of identified pdSNVs/pdCNVs according to the ACMG guidelines led to a molecular diagnosis in 19/144 cases, but this figure represents a lower limit and is expected to increase thanks to further clarification of the role of likely pathogenic variants in new ASD/NDD candidates. In conclusion, our study strengthens the role of BRSK2 and other neurodevelopmental genes in ASD risk, highlights novel candidates and contributes to characterize the allelic diversity, mode of inheritance and phenotypic impact of de novo and inherited risk variants in ASD/NDD genes.

Experience of a 2-year spinal muscular atrophy NBS pilot study in Italy: towards specific guidelines and standard operating procedures for the molecular diagnosis.

BACKGROUND: Spinal muscular atrophy (SMA) is due to the homozygous absence of SMN1 in around 97% of patients, independent of the severity (classically ranked into types I-III). The high genetic homogeneity, coupled with the excellent results of presymptomatic treatments of patients with each of the three disease-modifying therapies available, makes SMA one of the golden candidates to genetic newborn screening (NBS) (SMA-NBS). The implementation of SMA in NBS national programmes occurring in some countries is an arising new issue that the scientific community has to address. We report here the results of the first Italian SMA-NBS project and provide some proposals for updating the current molecular diagnostic scenario. METHODS: The screening test was performed by an in-house-developed qPCR assay, amplifying SMN1 and SMN2. Molecular prognosis was assessed on fresh blood samples. RESULTS: We found 15 patients/90885 newborns (incidence 1:6059) having the following SMN2 genotypes: 1 (one patient), 2 (eight patients), 2+c.859G>C variant (one patient), 3 (three patients), 4 (one patient) or 6 copies (one patient). Six patients (40%) showed signs suggestive of SMA at birth. We also discuss some unusual cases we found. CONCLUSION: The molecular diagnosis of SMA needs to adapt to the new era of the disease with specific guidelines and standard operating procedures. In detail, SMA diagnosis should be felt as a true medical urgency due to therapeutic implications; SMN2 copy assessment needs to be standardised; commercially available tests need to be improved for higher SMN2 copies determination; and the SMN2 splicing-modifier variants should be routinely tested in SMA-NBS.

3'UTR Deletion of NONO Leads to Corpus Callosum Anomaly, Left Ventricular Non-Compaction and Ebstein's Anomaly in a Male Fetus.

NONO (Non-Pou Domain-Containing Octamer-Binding Protein) gene maps on chromosome Xq13.1 and hemizygous loss-of-function nucleotide variants are associated with an emerging syndromic form of intellectual developmental disorder (MRXS34; MIM #300967), characterized by developmental delay, intellectual disability, poor language, dysmorphic facial features, and microcephaly. Structural brain malformation, such as corpus callosum and cerebellar abnormalities, and heart defects, in particular left ventricular non-compaction (LVNC), represent the most recurrent congenital malformations, recorded both in about 80% of patients, and can be considered the distinctive imaging findings of this disorder. We present on a further case of NONO-related disease; prenatally diagnosed in a fetus with complete corpus callosum agenesis; absence of septum pellucidum; pericallosal artery; LVNC and Ebstein's anomaly. A high-resolution microarray analysis demonstrated the presence of a deletion affecting the NONO 3'UTR; leading to a marked hypoexpression of the gene and the complete absence of the protein in cultured amniocytes. This case expands the mutational spectrum of MRXS34, advises to evaluate NONO variants in pre- and postnatal diagnosis of subjects affected by LVNC and other heart defects, especially if associated with corpus callosum anomalies and confirm that CNVs (Copy Number Variants) represent a non-negligible cause of Mendelian disorders.

Phenotypic Spectrum and Molecular Findings in 17 ATR-X Syndrome Italian Patients: Some New Insights.

ATR-X syndrome is a rare X-linked congenital disorder caused by hypomorphic mutations in the ATRX gene. A typical phenotype is well defined, with cognitive impairment, characteristic facial dysmorphism, hypotonia, gastrointestinal, skeletal, urogenital, and hematological anomalies as characteristic features. With a few notable exceptions, general phenotypic differences related to specific ATRX protein domains are not well established and should not be used, at least at the present time, for prognostic purposes. The phenotypic spectrum and genotypic correlations are gradually broadening, mainly due to rapidly increasing accessibility to NGS. In this scenario, it is important to continue describing new patients, illustrating the mode and age of onset of the typical and non-typical features, the classical ones and those tentatively added more recently. This report of well-characterized and mostly unreported patients expands the ATR-X clinical spectrum and emphasizes the importance of better clinical delineation of the condition. We compare our findings to those of the largest ATR-X series reported so far, discussing possible explanations for the different drawn conclusions.

Neurological assessment of newborns with spinal muscular atrophy identified through neonatal screening.

The possibility to identify patients with spinal muscular atrophy through neonatal screenings has highlighted the need for clinical assessments that may systematically evaluate the possible presence of early neurological signs. The aim of this study was to use the Hammersmith Neonatal Neurological Examination (HNNE) and a module specifically designed for floppy infants to assess the possible variability of neurological findings in infants identified through neonatal screening. The infants included in this study were identified as part of a pilot study exploring neonatal screening in two Italian regions. A neurological examination was performed using the HNNE and an additional module developed for the assessment of floppy infants. Seventeen infants were identified through the screening. One patient had 1 SMN2 copy, 9 had 2 copies, 3 had 3, and 4 had more than 3 copies. Nine of the 17 infants (53%) had completely normal results on both scales, 3 had minimal signs, and the other 5 had more obvious clinical signs. The number of SMN2 copies was related to the presence of abnormal neurological signs (p = 0.036) but two SMN2 copies were associated with variable clinical signs as they were found in some infants with respectively normal examination or obvious severe early signs. CONCLUSIONS: Our results suggest that the combination of both scales increases the possibility to detect neonatal neurological signs and to define different early patterns of involvement also identifying paucisymptomatic patients. WHAT IS KNOWN: • The use of new therapeutic options in presymptomatic SMA patients leads to a dramatic reduction of the onset and severity of the diesease. • The already existing tools commonly used in Type I SMA (HINE and CHOP-intend) may not be suitable to identify minor neurological signs in the neonatal period. WHAT IS NEW: • Combining the HNNE and the floppy infant module, we were able to identify early neurological signs in SMA infants identified through newborn screening and may help to predict the individual therapeutic outcome of these patients. • Iinfants with 2 SMN2 copies identified through the screening had a more variable neonatal examination compared to those with three or more copies, in agreement with similar findings in older infants.

Neuroacanthocytosis Syndromes in an Italian Cohort: Clinical Spectrum, High Genetic Variability and Muscle Involvement.

Neuroacanthocytosis (NA) syndromes are a group of genetically defined diseases characterized by the association of red blood cell acanthocytosis, progressive degeneration of the basal ganglia and neuromuscular features with characteristic persistent hyperCKemia. The main NA syndromes include autosomal recessive chorea-acanthocytosis (ChAc) and X-linked McLeod syndrome (MLS). A series of Italian patients selected through a multicenter study for these specific neurological phenotypes underwent DNA sequencing of the VPS13A and XK genes to search for causative mutations. Where it has been possible, muscle biopsies were obtained and thoroughly investigated with histochemical assays. A total of nine patients from five different families were diagnosed with ChAC and had mostly biallelic changes in the VPS13A gene (three nonsense, two frameshift, three splicing), while three patients from a single X-linked family were diagnosed with McLeod syndrome and had a deletion in the XK gene. Despite a very low incidence (only one thousand cases of ChAc and a few hundred MLS cases reported worldwide), none of the 8 VPS13A variants identified in our patients is shared by two families, suggesting the high genetic variability of ChAc in the Italian population. In our series, in line with epidemiological data, McLeod syndrome occurs less frequently than ChAc, although it can be easily suspected because of its X-linked mode of inheritance. Finally, histochemical studies strongly suggest that muscle pathology is not simply secondary to the axonal neuropathy, frequently seen in these patients, but primary myopathic alterations can be detected in both NA syndromes.

Chromosome 14 deletions, rings, and epilepsy genes: A riddle wrapped in a mystery inside an enigma.

The ring 14 syndrome is a rare condition caused by the rearrangement of one chromosome 14 into a ring-like structure. The formation of the ring requires two breakpoints and loss of material from the short and long arms of the chromosome. Like many other chromosome syndromes, it is characterized by multiple congenital anomalies and developmental delays. Typical of the condition are retinal anomalies and drug-resistant epilepsy. These latter manifestations are not found in individuals who are carriers of comparable 14q deletions without formation of a ring (linear deletions). To find an explanation for this apparent discrepancy and gain insight into the mechanisms leading to seizures, we reviewed and compared literature cases of both ring and linear deletion syndrome with respect to both their clinical manifestations and the role and function of potentially epileptogenic genes. Knowledge of the epilepsy-related genes in chromosome 14 is an important premise for the search of new and effective drugs to combat seizures. Current clinical and molecular evidence is not sufficient to explain the known discrepancies between ring and linear deletions.

Lynch syndrome with exclusive skin involvement: time to consider a molecular definition?

Muir-Torre syndrome (MTS) is clinically characterized by the occurrence of skin, usually sebaceous, and visceral tumors in the same individual. The most common underlying mechanism is a constitutional defect of the mismatch repair (MMR) genes that cause Lynch syndrome (LS). Herewithin we report on a 76 years-old male patient heterozygous for a pathogenic MSH2 missense substitution who presented with a striking cutaneous phenotype in the absence of typical LS visceral tumors. The patient developed 20 skin tumors, including sebaceous adenomas/carcinomas and keratoacanthomas. Two skin tumors showed immunohistochemical loss of MSH2 and MSH6 expression. There was no apparent family history of neoplasia. Based on the variable involvement of the skin and internal organs, we suggest that the definition of tumor associations that are often observed as variants of inherited tumor syndromes, such as MTS, should be guided by the underlying molecular bases. In addition, the presence of multiple sebaceous tumors, especially if showing MMR deficiency, appears to be a very strong indicator of a constitutional MMR gene defect. The reasons underlying the high phenotypic variability of cutaneous phenotypes associated with constitutional MMR defects are yet to be determined.

A novel truncating variant within exon 7 of KAT6B associated with features of both Say-Barber-Bieseker-Young-Simpson syndrome and genitopatellar syndrome: Further evidence of a continuum in the clinical spectrum of KAT6B-related disorders.

KAT6B sequence variants have been identified in both patients with the Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) and in the genitopatellar syndrome (GPS). In SBBYSS, they were reported to affect mostly exons 16-18 of KAT6B, and the predicted mechanism of pathogenesis was haploinsufficiency or a partial loss of protein function. Truncating variants in KAT6B leading to GPS appear to cluster within the proximal portion of exon 18, associated with a dominant-negative effect of the mutated protein, most likely. Although SBBYSS and GPS have been initially considered allelic disorders with distinctive genetic and clinical features, there is evidence that they represent two ends of a spectrum of conditions referable as KAT6B-related disorders. We detected a de novo truncating variant within exon 7 of KAT6B in a 8-year-old female who presented with mild intellectual disability, facial dysmorphisms highly consistent with SBBYSS, and skeletal anomalies including exostosis, that are usually considered component manifestations of GPS. Following the clinical diagnosis driven by the striking facial phenotype, we analyzed the KAT6B gene by NGS techniques. The present report highlights the pivotal role of clinical genetics in avoiding clear-cut genotype-phenotype categories in syndromic forms of intellectual disability. In addition, it further supports the evidence that a continuum exists within the clinical spectrum of KAT6B-associated disorders.

Guideline recommendations for diagnosis and clinical management of Ring14 syndrome-first report of an ad hoc task force.

BACKGROUND: Ring chromosome 14 syndrome is a rare chromosomal disorder characterized by early onset refractory epilepsy, intellectual disability, autism spectrum disorder and a number of diverse health issues. RESULTS: The aim of this work is to provide recommendations for the diagnosis and management of persons affected by ring chromosome 14 syndrome based on evidence from literature and experience of health professionals from different medical backgrounds who have followed for several years subjects affected by ring chromosome 14 syndrome. The literature search was performed in 2016. Original papers, meta-analyses, reviews, books and guidelines were reviewed and final recommendations were reached by consensus. CONCLUSION: Conventional cytogenetics is the primary tool to identify a ring chromosome. Children with a terminal deletion of chromosome 14q ascertained by molecular karyotyping (CGH/SNP array) should be tested secondarily by conventional cytogenetics for the presence of a ring chromosome. Early diagnosis should be pursued in order to provide medical and social assistance by a multidisciplinary team. Clinical investigations, including neurophysiology for epilepsy, should be performed at the diagnosis and within the follow-up. Following the diagnosis, patients and relatives/caregivers should receive regular care for health and social issues. Epilepsy should be treated from the onset with anticonvulsive therapy. Likewise, feeding difficulties should be treated according to need. Nutritional assessment is recommended for all patients and nutritional support for malnourishment can include gastrostomy feeding in selected cases. Presence of autistic traits should be carefully evaluated. Many patients with ring chromosome 14 syndrome are nonverbal and thus maintaining their ability to communicate is always essential; every effort should be made to preserve their autonomy.

Simpson-Golabi-Behmel syndrome in a female: A case report and an unsolved issue.

Simpson-Golabi-Behmel syndrome is an X-linked recessive overgrowth condition caused by alterations in GPC3 gene, encoding for the cell surface receptor glypican 3, whose clinical manifestations in affected males are well known. Conversely, there is little information regarding affected females, with very few reported cases, and a clinical definition of this phenotype is still lacking. In the present report we describe an additional case, the first to receive a primary molecular diagnosis based on strong clinical suspicion. Possible explanations for full clinical expression of X-linked recessive conditions in females include several mechanisms, such as skewed X inactivation or homozygosity/compound heterozygosity of the causal mutation. Both of these were excluded in our case. Given that the possibility of full expression of SGBS in females is now firmly established, we recommend that GPC3 analysis be performed in all suggestive female cases. © 2016 Wiley Periodicals, Inc.