Phenotype and Genotype of Children with ALS2 gene-Related Disorder.

INTRODUCTION: The Alsin Rho Guanine Nucleotide Exchange Factor (ALS2) gene encodes a protein alsin that functions as a guanine nucleotide exchange factor. The variations in ALS2 gene leads to degeneration of upper motor neurons of the corticospinal tract. The phenotypes resulting from variants in ALS2 gene are infantile-onset ascending hereditary spastic paralysis (IAHSP, OMIM # 607225), juvenile primary lateral sclerosis (JPLS, OMIM # 606353), and juvenile amyotrophic lateral sclerosis (JALS, OMIM # 205100). Our study objectives were to describe the clinical phenotype and genotype of children with an established diagnosis of ALS2 gene-related disorder. METHODS: The clinical details, laboratory data, and genotype findings of children with an established diagnosis of ALS2 gene-related disorder were collected from the hospital electronic database after obtaining institutional review board approval. RESULTS: One family with three affected siblings, a second family with a proband and an affected fetus, and a third family with two affected siblings with ALS2 gene variants were identified. IAHSP was diagnosed in all of our patients with variants in ALS2 gene. The clinical findings observed in our patients were insidious onset progressive spastic paraparesis, contractures, and dysarthria. Nonsense variants were observed in four patients while frameshift variant was observed in one family. Novel variants in ALS2 gene were identified in two unrelated families. CONCLUSION: ALS2 mutation results in rare neurodegenerative disorders with the clinical spectrum encompassing IAHSP, JPLS, and JALS disorders. In view of allelic heterogeneity described in the literature, more research studies are needed for establishing genotype-phenotype correlation in patients with ALS2 gene-related disorder.

Advocating Targeted Sequential Screening over Whole Exome Sequencing in 21-Hydroxylase Deficiency.

OBJECTIVES: Whole exome sequencing (WES) has emerged as the preferred method for diagnosing a range of Mendelian disorders. Nonetheless, the applicability of WES in genetic diagnosis of 21-hydroxylase deficiency (21-OHD) remains uncertain due to the intricacies involved in molecular analysis of the CYP21A2 gene. METHODS: In this case series, authors report the outcomes of couples or families who underwent WES followed by focused sequential strategy (FSS) targeting CYP21A2 gene hotspot mutations and targeted sequencing of genes associated with Congenital Adrenal Hyperplasia (CAH). RESULTS: This analysis revealed that WES, when compared to FSS, resulted in six false-negative findings out of seven subjects and one false-positive result. These results were corroborated through validation using Multiplex Ligation-Dependent Probe Amplification (MLPA) and Sanger sequencing. CONCLUSIONS: One major limitation of exome sequencing lies in target enrichment, which often achieves less than 95% coverage of the regions of interest, potentially leading to false negatives. This challenge is particularly pronounced when deciphering the complex genetics of 21-OHD, characterized by intricate pseudogene-derived rearrangements and gene conversions. Additionally, next-generation sequencing (NGS) analysis of the CYP21A2 gene is not straightforward due to reads aligning to pseudogene regions, necessitating stringent computational pipelines with defined targets. However, simple genotyping assays have shown a high positive yield of pseudogene-derived mutations in over 80% of cases, while targeted NGS can be valuable in subjects with initially negative results. Therefore, WES is not recommended as the primary testing method for 21-OHD and may be better suited for rare forms of CAH once CYP21A2 mutations have been ruled out.

CFTR mutations and phenotypic correlations in people with cystic fibrosis: a retrospective study from a single centre in south India.

Background: Emerging data reveal higher-than-expected prevalence of cystic fibrosis (CF) among non-European populations worldwide including in the Indian subcontinent. Systematic analyses of the CFTR mutation profile, and genotype-phenotype correlations among people with CF from south, east, or northeast India have not been reported before. We wanted to identify CFTR mutations in people with CF, and highlight novel variants, selective phenotypic correlations, and regional variances within India. Methods: A retrospective study was conducted at Christian Medical College, Vellore, India (single tertiary referral hospital) from September 2010 to August 2022, involving 120 people with CF from (i) four south Indian states (Tamil Nadu, Andhra Pradesh, Kerala, Karnataka), (ii) in and nearby regions of West Bengal, India and (iii) Bangladesh. Comprehensive CFTR mutation analyses were done by Next-Generation Sequencing, and variants were categorized per American College of Medical Genetics guidelines and compared with validated Locus-specific databases. Demographic characteristics, mutation profile, novel mutations, selective phenotype correlations, and regional variances were assessed. Findings: In 120 people with CF, 55 CFTR variants were identified, including six novel variants. F508del was the predominant mutation, yet with a lower allele frequency than reported among European populations (27% versus 70%). Phenotypic correlations suggested high mutational pathogenicity causing severe multi-organ morbidity, and death in 27%. Milder variants associated with pancreatic sufficiency were also evident in 23% of people with CF. Statistically significant regional variances were noted in genotype frequency, and clinical phenotype among people with CF from the two regions. Hotspot exons and introns that could potentially help create targeted mutation panels were identified. Interpretation: The identification of 55 different CFTR variants among 120 people with CF describes the diversity of mutations noted in India, while also revealing the challenges that providers may encounter in timely diagnosis and treatment of CF. However, these single-centre data have specific limitations and cannot be generalised to all people with CF from India or to those of non-European origin. Our data on regional CFTR mutations contribute to the emerging national registry on CF epidemiology in India, help formulate diagnostic and newborn screening algorithms, help optimise clinical care, and highlight urgency to improve access to life-changing modulator therapy. Funding: Cystic Fibrosis Foundation, USA (towards the CF-India Demonstration Project) and Christian Medical College, Vellore, India.

A pilot study of childhood-onset Takayasu arteritis using whole exome sequencing suggests oligogenic inheritance involving classical complement, collagen, and autoinflammatory pathways.

Takayasu arteritis (TA) is a chronic granulomatous inflammatory disease affecting the aorta and its branches. Paediatric TA (pTA) may present from 6 months after birth till the adolescent age group. Genetics and pathogenesis of pTA are not fully understood. Earlier studies reported monogenic mutation in NOD2, XIAP, and STAT1 genes in patients with pTA. TA, a relatively rare disease, is more common in geographical pockets, including India. We hypothesized that South Asian patients with pTA, namely, those of Indian subcontinent origin, may have clinically relevant and unique pathogenic variants involving one or more genes, especially those linked to genetically driven vasculitic illnesses, including autoinflammatory pathologies. Children with pTA fulfilling EULAR/PRINTO/PReS classification criteria and presenting with clinical symptoms to the Paediatric Rheumatology clinic of Christian Medical College, Vellore, were included. Blood samples were collected after getting informed consent from parents or guardians and assent forms from children. DNA was extracted from whole blood using the Qiagen DNA extraction kit. Initially, the common variant in Indian population, namely, ADA2 c.139G > A; p.Gly47Arg, was screened, followed by whole exome sequencing. Fourteen children were recruited for the study. Median age of patients was 11 years (4 months-14 years) with a male-to-female ratio of 4:10. Distribution of angiographic subsets by Numano's classification of included children were as follows: type 5 (n = 7), type 4 (n = 5), and type 3 (n = 2). We identified novel variants in ten different genes. This include variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. Two of 14 patients have heterozygous pathogenic variants; this implies that combination of heterozygous variants in C3 and COL5A1 might lead to disease development, suggesting digenic inheritance. One patient has a homozygous variant in CYBA. None of the patients were identified to have ADA2 variants. Whole exome sequencing reveals combination of rare variants in genes C3, COL5A1, and CYBA associated with disease development in children with Takayasu Arteritis. Key Points • We identified novel variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. • Two of 14 patients have heterozygous pathogenic variants in C3 and COL5A1; this may have implications in disease development, suggesting digenic inheritance. • One patient has homozygous variant in CYBA. • None of the patients were identified to have ADA2 variants.

Exploring the clinical utility of exome sequencing/Mono, Duo, Trio in prenatal testing: a retrospective study in a tertiary care centre in South India.

OBJECTIVES: With the availability of Next Generation Sequencing (NGS) diagnosis of genetic disorders has improved significantly. Its use is also applicable to ascertain diagnosis and management in a perinatal setting. The study aims to detect the genetic aetiology of various congenital structural and functional defects using NGS technology in the reproductive cohort at a tertiary centre. The secondary objective is to address challenges in the interpretation of variants. METHODS: This was a retrospective study of couples who underwent exome sequencing (Mono-testing proband only or Duo-testing parents only or Trio-testing proband and parents) for suspected single gene disorders between years 2020-2022 at a tertiary care perinatal center in the South India. American College of Medical Genetics (ACMG) guidelines were followed to classify the pathogenicity of the variants identified by exome sequencing. RESULTS: The overall diagnostic yield as defined by pathogenic/likely pathogenic variants obtained was (23/43) 53.4 %. The individual subsets have the following diagnostic yield viz., Mono 5/6 (83 %); Carrier 16/32 (50 %); Trio 2/5 (40 %). Diagnostic yield was significantly higher in consanguineous couples. However, miscarriage history, and organ system involvement did not have a significant effect on the diagnostic yield. Prenatal diagnosis was offered for seven patients based on the exome result. One fetus was confirmed with a compound heterozygous pathogenic variant. CONCLUSIONS: Diagnostic yield of exome sequencing in our cohort was 53 %. The detection of pathogenic variants was maximum in those cases undergoing Mono exome sequencing. In places where there is a high prevalence of consanguinity and endogamy, NGS may be offered as first line test in the context of prenatal diagnosis.

High carrier frequency of CYP21A2 gene mutations in Southern India - underscoring the need for genetic testing in Congenital Adrenal Hyperplasia.

PURPOSE: Congenital Adrenal Hyperplasia (CAH) is one of the highly prevalent autosomal recessive endocrine disorders. The majority of CAH cases result from mutations in the CYP21A2 gene, leading to 21-hydroxylase deficiency. However, with the pseudogene-associated challenges in CYP21A2 gene analysis, routine genetic diagnostics and carrier screening in CAH are not a part of the first-tier investigations in a clinical setting. Furthermore, there is a lack of data on the carrier frequency for 21-OH deficiency. Therefore, this study is aimed at investigating the carrier frequency of common pseudogene derived CYP21A2 mutations in Southern India. METHODS: Recently, a cost-effective Allele-specific PCR based genotyping for CYP21A2 hotspot mutations has been demonstrated to be a highly specific and sensitive assay at the authors' center. Leveraging this approach, a total of 1034 healthy individuals from South India underwent screening to identify the carrier frequency of nine hotspot mutations in the CYP21A2 gene. RESULTS: In this study, it was observed that 9.76% of the subjects were carriers for one or more of the nine different CYP21A2 mutations. Among the carriers, the most common was the large 30 kb deletion, followed by II72N, E6 CLUS, and I2G mutations. CONCLUSION: We have identified a high prevalence of CYP21A2 mutation carriers in Southern India. These findings emphasize the importance of implementing and expanding cost-effective genetic diagnostics and carrier screening throughout India. Such initiatives would play a crucial role in managing the disease burden, enabling early intervention, and establishing guidelines for CAH newborn genetic screening in the country. This study represents the first carrier screening data on CYP21A2 hotspot mutations from India and is the largest study conducted till date in this context.

Investigation of mutation spectrum amongst patients with familial primary cardiomyopathy using targeted NGS in Indian population.

Genetic cardiomyopathies (CM) are disorders that affect morphology and function of cardiac muscle. Significant number of genes have been implicated in causing the phenotype. It is one of the leading genetic causes of death in young. We performed a study to understand the genetic variants in primary cardiomyopathies in an Indian cohort. Study comprised of 22 probands (13 with family history) representing hypertrophic (n = 10), dilated (n = 7), restrictive (n = 2) and arrhythmogenic ventricular(n = 3) cardiomyopathies. Genomic DNA was target captured with a panel of 46 genes and libraries sequenced on Illumina platform. Analysis identified, reported pathogenic as well as novel pathogenic (n = 6) variants in 16 probands. Of the 10 HCM patients, candidate variants were identified in nine of them involving sarcomere genes (62%, MYBPC3, MYH6, MYH7, MYL3, TTN), Z-disc (10%, ACTN2, LDB3, NEXN,), desmosome (10%, DSG2, DSP, PKP2) cytoskeletal (4%, DTNA) and ion channel (10% RYR2). In four DCM patients, variants were identified in genes NEXN, LMNA and TTN. Three arrhythmogenic right ventricular cardiomyopathy (ARVD) patients carried mutations in desmosome genes. Rare TTN variants were identified in multiple patients. Targeted capture and sequencing resulted in identification of candidate variants in about 70% of the samples which will help in management of disease in affected individual as well as in screening and early diagnosis in asymptomatic family members. Amongst the analysed cases, 22% were inconclusive without any significant variant identified. Study illustrates the utility of next-generation multi-gene panel as a cost-effective genetic testing to screen all forms of primary cardiomyopathies.

Homozygous CARD14 variant presenting as infantile erythroderma.

A wide range of inherited and acquired conditions can manifest as infantile erythroderma, among which CARD14-associated papulosquamous eruption (CAPE) is a rare cause. An infant boy presented with a psoriasiform rash that progressed to erythroderma and was unresponsive to topical steroids and cyclosporine. The early onset of the disease, its severity and resistance to conventional treatment were suggestive of a genetic cause. Genetic evaluation revealed a homozygous CARD14 variant of uncertain significance establishing the diagnosis of CAPE, and his parents were heterozygous carriers. There was only minimal improvement in the condition with supportive management and treatment with acitretin. Unfortunately, the child succumbed to sepsis and metabolic complications following a sudden worsening of skin disease. This case highlights the significance of genetic studies in diagnosing treatment-refractory cases of infantile erythroderma and emphasises the importance of early recognition of this rare condition.

KCTD7-related progressive myoclonic epilepsy: Report of 42 cases and review of literature.

OBJECTIVE: KCTD7-related progressive myoclonic epilepsy (PME) is a rare autosomal-recessive disorder. This study aimed to describe the clinical details and genetic variants in a large international cohort. METHODS: Families with molecularly confirmed diagnoses of KCTD7-related PME were identified through international collaboration. Furthermore, a systematic review was done to identify previously reported cases. Salient demographic, epilepsy, treatment, genetic testing, electroencephalographic (EEG), and imaging-related variables were collected and summarized. RESULTS: Forty-two patients (36 families) were included. The median age at first seizure was 14 months (interquartile range = 11.75-22.5). Myoclonic seizures were frequently the first seizure type noted (n = 18, 43.9%). EEG and brain magnetic resonance imaging findings were variable. Many patients exhibited delayed development with subsequent progressive regression (n = 16, 38.1%). Twenty-one cases with genetic testing available (55%) had previously reported variants in KCTD7, and 17 cases (45%) had novel variants in KCTD7 gene. Six patients died in the cohort (age range = 1.5-21 years). The systematic review identified 23 eligible studies and further identified 59 previously reported cases of KCTD7-related disorders from the literature. The phenotype for the majority of the reported cases was consistent with a PME (n = 52, 88%). Other reported phenotypes in the literature included opsoclonus myoclonus ataxia syndrome (n = 2), myoclonus dystonia (n = 2), and neuronal ceroid lipofuscinosis (n = 3). Eight published cases died over time (14%, age range = 3-18 years). SIGNIFICANCE: This study cohort and systematic review consolidated the phenotypic spectrum and natural history of KCTD7-related disorders. Early onset drug-resistant epilepsy, relentless neuroregression, and severe neurological sequalae were common. Better understanding of the natural history may help future clinical trials.

Angiogenesis related genes in Takayasu Arteritis (TAK): robust association with Tag SNPs of IL-18 and FGF-2 in a South Asian Cohort.

We performed genetic association study for genes encoding angiogenic and angiostatic proteins in patients with Takayasu arteritis (TAK). A total of 96 SNPs involving 60 genes were studied. Genotyping was performed in Fluidigm 96.96 Dynamic Array chip. All statistical analysis for SNP evaluation was performed using PLINK software. Initial analyses revealed five SNPs from three genes [IL-18 (encodes Interleukin-18), FGF2 (encodes Fibroblast Growth Factor-2), and ANGPT1 (encodes Angiopoietin-1)] as significantly different between controls and cases (uncorrected p < 0.05). After permutation-based analysis, two tag SNPs on the promoter region of IL-18 (rs187238 and rs1946518) and one 3'UTR tag SNP (rs1476217) of FGF2 were significantly associated with susceptibility to TAK, with p and OR (95% CI) of 0.0006 and 1.64 (1.25-2.17), 0.03 and 1.28 (1.02-1.64) & 0.016 and 1.33 (1.05-1.67), respectively; while, the two tag SNPs of ANGPT1 gene (rs6469101 and rs16875900) showed a trend (p = 0.055 & p = 0.051, respectively after permutation based correction). There is robust linkage disequilibrium between the two tag SNPs of IL-18 gene as validated by 1000 genome data of South Asian population; the eQTL effects of these tag SNPs of IL-18 and FGF2 genes on adjacent genes further suggest that these tag SNPs act as genetic risks for development of TAK in South Asians, with possible functional implications towards future biomarker development. Genotype phenotype study by genetic model-based analysis also revealed associations between genotype subsets and clinical features like fever, visual loss, left subclavian and coronary artery involvement in our TAK patients.

Diagnostic exome identifies a novel PRKG2 mutation in a proband with skeletal dysplasia.

This graphic abstract combines pedigree, dysmorphology features, radiographs, and the PRKG2 protein domain, specifically the CNB-A regulatory domain, which harbors a mutation resulting in premature protein termination.

Landscape of genetic infantile epileptic spasms syndrome-A multicenter cohort of 124 children from India.

OBJECTIVE: Literature on the genotypic spectrum of Infantile Epileptic Spasms Syndrome (IESS) in children is scarce in developing countries. This multicentre collaboration evaluated the genotypic and phenotypic landscape of genetic IESS in Indian children. METHODS: Between January 2021 and June 2022, this cross-sectional study was conducted at six centers in India. Children with genetically confirmed IESS, without definite structural-genetic and structural-metabolic etiology, were recruited and underwent detailed in-person assessment for phenotypic characterization. The multicentric data on the genotypic and phenotypic characteristics of genetic IESS were collated and analyzed. RESULTS: Of 124 probands (60% boys, history of consanguinity in 15%) with genetic IESS, 105 had single gene disorders (104 nuclear and one mitochondrial), including one with concurrent triple repeat disorder (fragile X syndrome), and 19 had chromosomal disorders. Of 105 single gene disorders, 51 individual genes (92 variants including 25 novel) were identified. Nearly 85% of children with monogenic nuclear disorders had autosomal inheritance (dominant-55.2%, recessive-14.2%), while the rest had X-linked inheritance. Underlying chromosomal disorders included trisomy 21 (n = 14), Xq28 duplication (n = 2), and others (n = 3). Trisomy 21 (n = 14), ALDH7A1 (n = 10), SCN2A (n = 7), CDKL5 (n = 6), ALG13 (n = 5), KCNQ2 (n = 4), STXBP1 (n = 4), SCN1A (n = 4), NTRK2 (n = 4), and WWOX (n = 4) were the dominant single gene causes of genetic IESS. The median age at the onset of epileptic spasms (ES) and establishment of genetic diagnosis was 5 and 12 months, respectively. Pre-existing developmental delay (94.3%), early age at onset of ES (<6 months; 86.2%), central hypotonia (81.4%), facial dysmorphism (70.1%), microcephaly (77.4%), movement disorders (45.9%) and autistic features (42.7%) were remarkable clinical findings. Seizures other than epileptic spasms were observed in 83 children (66.9%). Pre-existing epilepsy syndrome was identified in 21 (16.9%). Nearly 60% had an initial response to hormonal therapy. SIGNIFICANCE: Our study highlights a heterogenous genetic landscape and phenotypic pleiotropy in children with genetic IESS.

Clinico-Etiological Spectrum and Functional Outcomes of Children with Pre-Status Dystonicus and Status Dystonicus (SD): A Descriptive Study.

Background: Status dystonicus (SD) is a life-threatening movement disorder emergency characterized by increasingly frequent and severe episodes of generalized dystonia, requiring urgent hospital admission. The diverse clinico-etiological spectrum, high risk of recurrence, and residual disabilities complicate functional outcomes. Aim: We aim to describe the clinico-etiological spectrum, radiology, therapeutic options, and follow-up of patients with pre-status dystonicus (pre-SD) and SD. Methodology: A cross-sectional retrospective study was carried out in a tertiary care referral center. The clinical, laboratory, and radiology data of all patients aged less than 18 years with pre-SD and SD from January 2010 to December 2020 were collected. The Dystonia Severity Assessment Plan (DSAP) scale for grading severity and the modified Rankin Scale (mRS) for assessing outcome were used at the last follow-up visit. Results: Twenty-eight patients (male:female: 2.1:1) experiencing 33 episodes of acute dystonia exacerbation were identified. The median age at the onset of dystonia and SD presentation was 8.71 (range: 0.25-15.75) and 9.12 (range: 1-16.75) years, respectively. Four patients experienced more than one episode of SD. The etiological spectrum of SD includes metabolic (Wilson's disease-13, L-aromatic amino acid decarboxylase deficiency-one, and Gaucher's disease-one), genetic (neurodegeneration with brain iron accumulation-three and KMT2B and THAP 1 gene-related-one each), structural-three, post-encephalitic sequelae (PES)-four, and immune-mediated (anti-NMDA receptor encephalitis-one). Five patients had pre-SD (DSAP grade 3), and 23 patients had established SD (DSAP grade 4-17 and DSAP grade 5-six). The Rapid escalation of chelation therapy precipitated SD in 11 patients with Wilson's disease. Febrile illness or pneumonia precipitated SD in nine patients. Twenty-three episodes of SD required midazolam infusion in addition to anti-dystonic medications. The median duration of hospital stay was 10 days (range: 3-29). Twenty-three patients had resolution of SD but residual dystonia persisted, while two patients had no residual dystonia at follow-up. Three patients succumbed owing to refractory SD and its complications. Conclusion: Early identification of triggers, etiology, and appropriate management are essential to calm the dystonic storm.

Adult-onset leukodystrophies: a practical guide, recent treatment updates, and future directions.

Adult-onset leukodystrophies though individually rare are not uncommon. This group includes several disorders with isolated adult presentations, as well as several childhood leukodystrophies with attenuated phenotypes that present at a later age. Misdiagnoses often occur due to the clinical and radiological overlap with common acquired disorders such as infectious, immune, inflammatory, vascular, metabolic, and toxic etiologies. Increased prevalence of non-specific white matter changes in adult population poses challenges during diagnostic considerations. Clinico-radiological spectrum and molecular landscape of adult-onset leukodystrophies have not been completely elucidated at this time. Diagnostic approach is less well-standardized when compared to the childhood counterpart. Absence of family history and reduced penetrance in certain disorders frequently create a dilemma. Comprehensive evaluation and molecular confirmation when available helps in prognostication, early initiation of treatment in certain disorders, enrollment in clinical trials, and provides valuable information for the family for reproductive counseling. In this review article, we aimed to formulate an approach to adult-onset leukodystrophies that will be useful in routine practice, discuss common adult-onset leukodystrophies with usual and unusual presentations, neuroimaging findings, recent advances in treatment, acquired mimics, and provide an algorithm for comprehensive clinical, radiological, and genetic evaluation that will facilitate early diagnosis and consider active treatment options when available. A high index of suspicion, awareness of the clinico-radiological presentations, and comprehensive genetic evaluation are paramount because treatment options are available for several disorders when diagnosed early in the disease course.

Childhood Neurological Disorders With Hyperhomocystinemia: A Case-Based Review.

Hyperhomocysteinemia is a rare neurometabolic syndrome with diverse manifestations in the pediatric age group, thereby posing a diagnostic challenge. Biochemical testing is imperative to guide plan of evaluation, which may include appropriate genetic testing, in inherited disorders. Through this case-based approach, we demonstrate the heterogeneity of clinical presentation, biochemical and genetic evaluation, and treatment strategies that may reverse this condition among children.

SERPINF1 gene variants causing late-onset progressive deforming osteogenesis imperfecta - A study of 18 patients from India.

SERPINF1 gene variants lead to a severe type of osteogenesis imperfecta (OI) attributed to defects in the matrix mineralization. We present 18 patients with SERPINF1 gene variants leading to severe progressive deforming OI, the largest series in the world to date. These patients were normal at birth and had the first fracture between 2 months to 9 years; progression of deformities was seen in 12 adolescents who became nonambulatory. Radiologically, compression fractures with kyphoscoliosis, protrusio acetabuli, and lytic lesions in the metaphysis and pelvis were seen in older children with classical popcorn appearance in the distal femoral metaphysis in three. By exome sequencing and targeted sequencing, we identified ten variants. One was unreported and novel; three other novel variants in this series were reported earlier. The recurrent deletion inframe mutation p.phe277del was found in 5 patients from three families. Alkaline phosphatase was elevated in all children on the first visit. Bone mineral density was low in all patients and showed improvement at two years in seven children on regular pamidronate therapy. For others, the 2 year BMD data were not available. The Z scores for four of the seven children showed worsening at the 2-year follow-up.

Exploration of clinical and genetic findings in Ataxia-Telangiectasia (AT) patients from the Indian subcontinent.

BACKGROUND: Ataxia-Telangiectasia (AT) is a rare autosomal recessive neurodegenerative disorder. It is caused by mutations in the Ataxia-Telangiectasia mutated (ATM) gene, which codes for protein ATM serine/threonine kinase. OBJECTIVE: We aim to describe the clinical and radiological findings in children and adolescents of 20 molecularly confirmed cases of AT. We aim to correlate these findings with the genotype identified among them. METHODS: This retrospective study included 20 patients diagnosed clinically and genetically with AT over 10 years. The clinical, radiological and laboratory data were extracted from the hospital's electronic medical records. Molecular testing was done using next generation sequencing and Sanger sequencing. In silico predictions were performed for the variants identified by applying Cryp-Skip, Splice site prediction by Neural Network, Mutation Taster and Hope prediction tool. RESULTS: Consanguinity was documented in nearly half of the patients. Telangiectasia was absent in 10%. Microcephaly was seen in 40% cases. The incidence of malignancy in our study population was low. Molecular testing done in the 18 families (20 patients) identified 23 variants of which ten were novel. Biallelic homozygous variants were noted in 13 families and compound heterozygous in 5 families. Out of the 13 families who were homozygous, 8 families (61.5%) (9 patients) have history of consanguinity. In silico prediction of novel missense variants, NM_000051.4 (ATM_v201): c.2702T > C showed disruption of the α-helix of ATM protein and NM_000051.4 (ATM_v201): c.6679C > G is expected to disturb the rigidity of protein structure in the FAT domain. The four novel splice site variants and two intronic variants result in exon skipping as predicted by Cryp-Skip. CONCLUSIONS: AT should be confirmed by molecular testing in young-onset cerebellar ataxia, even without telangiectasia. Awareness of this rare disease will facilitate study of larger cohorts from Indian population to characterize variants and determine its prevalence in this population.

Proband only exome sequencing in 403 Indian children with neurodevelopmental disorders: Diagnostic yield, utility and challenges in a resource-limited setting.

Whole exome sequencing is recommended as the first tier test for neurodevelopmental disorders (NDDs) with trio being an ideal option for the detection of de novo variants. Cost constraints have led to adoption of sequential testing i.e. proband-only whole exome followed by targeted testing of parents. The reported diagnostic yield for proband exome approach ranges between 31 and 53%. Typically, these study designs have aptly incorporated targeted parental segregation before concluding a genetic diagnosis to be confirmed. The reported estimates however do not accurately reflect the yield of proband only standalone whole -exome, a question commonly posed to the referring clinician in self pay medical systems like India. To assess the utility of standalone proband exome (without follow up targeted parental testing), we retrospectively evaluated 403 cases of neurodevelopmental disorders referred for proband-only whole exome sequencing at Neuberg Centre for Genomic Medicine (NCGM), Ahmedabad during the period of January 2019 and December 2021. A diagnosis was considered confirmed only upon the detection of Pathogenic/Likely Pathogenic variants in concordance with patient's phenotype as well as established inheritance pattern. Targeted parental/familial segregation analysis was recommended as a follow up test where applicable. The diagnostic yield of the proband-only standalone whole exome was 31.5%. Only 20 families submitted samples for follow up targeted testing, and a genetic diagnosis was confirmed in twelve cases increasing the yield to 34.5%. To understand factors leading to poor uptake of sequential parental testing, we focused on cases where an ultra-rare variant was detected in hitherto described de novo dominant neurodevelopmental disorder. A total of 40 novel variants in genes associated with de novo autosomal dominant disorders could not be reclassified as parental segregation was denied. Semi-structured telephonic interviews were conducted upon informed consent to comprehend reasons for denial. Major factors influencing decision making included lack of definitive cure in the detected disorders; especially when couples not planning further conception and financial constraints to fund further targeted testing. Our study thus depicts the utility and challenges of proband-only exome approach and highlights the need for larger studies to understand factors influencing decision making in sequential testing.

Clustering of Juvenile Canavan disease in an Indian community due to population bottleneck and isolation: genomic signatures of a founder event.

Mild/juvenile Canavan disease (M/JCD) is less frequently reported in the literature and little is known about its pathogenetic mechanisms. We report a comprehensive investigation into the pathogenetic mechanism of a novel NM_000049.4(ASPA):c.526G>A variant in two families. The families belong to Telugu Devanga Chettiar community (TDC) from southern India. TDC has a complex history of migration from their historical origin centuries ago with high endogamy. TDC probably has the highest clustering M/JCD recorded historically (around 24 cases). The pathogenic variant was shown to cause non-classical splicing defect resulting in two different transcripts. The splicing aberration, a loss of function mechanism coupled with a milder missense effect can explain the milder phenotype compared to the infantile-onset CD. The high clustering of an extremely rare form of neurodegenerative disorder with reduced fitness, led us to speculate the possibility of a founder event. Genotyping array of TDC and multiple distinct populations of Indian origin for several population genetic parameters was performed. It yielded robust signatures of a founder event in TDC, such as a high fixation index, increased runs of homozygosity and identity-by-descent in the absence of consanguinity; a large haplotype with high linkage disequilibrium among markers comprising the pathogenic variant; a robust population structure; mutation dating, estimating the age of the potential founder of TDC at around 375 years; possibly a high carrier rate in TDC. This study has not only focused its attention on natural history and pathogenetics but also paves way for carrier screening programs in TDC and future therapeutic studies.