Cri-du-Chat Syndrome: Revealing a Familial Atypical Deletion in 5p.

Introduction: Cri-du-chat syndrome is generally diagnosed when patients present a high-pitched cry at birth, microcephaly, ocular hypertelorism, and prominent nasal bridge. The karyotype is useful to confirm deletions in the short arm of chromosome 5 (5p-) greater than 10 Mb. In cases of smaller deletions, it is necessary to resort to other molecular techniques such as fluorescence in situ hybridization, multiplex ligation-dependent probe amplification (MLPA) or genomic array. Case Presentation: We report a family with an atypical deletion in 5p (mother and 2 children) and variable phenotypes compared with the literature. We applied a P064 MLPA kit to evaluate 5p- in the mother and the 2 children, and we used the Infinium CytoSNP-850K BeadChip genomic array to evaluate the siblings, an 11-year-old boy and a 13-year-old girl, to better define the 5p breakpoints. Both children presented a high-pitched cry at birth, but they did not present any of the typical physical features of 5p- syndrome. The MLPA technique with 5 probes for the 5p region revealed that the patients and their mother presented an atypical deletion with only 4 probes deleted (TERT_ex2, TERT_ex13, CLPTM1L, and IRX4). The genomic array performed in the siblings' samples revealed a 6.2-Mb terminal deletion in 5p15.33p15.32, which was likely inherited from their mother, who presented similar molecular features, seen in MLPA. Discussion: The sparing of the CTNND2 gene, which is associated with cerebral development, in both siblings may explain why these 2 patients had features such as better communication skills which most patients with larger 5p deletions usually do not present. In addition, both patients had smaller deletions than those found in patients with a typical 5p- phenotype. This report demonstrates the utility of genomic arrays as a diagnostic tool to better characterize atypical deletions in known syndromes such as 5p- syndrome, which will allow a better understanding of the genotype-phenotype correlations.

Phenotypic and mutational spectrum of ROR2-related Robinow syndrome.

Robinow syndrome is characterized by a triad of craniofacial dysmorphisms, disproportionate-limb short stature, and genital hypoplasia. A significant degree of phenotypic variability seems to correlate with different genes/loci. Disturbances of the noncanonical WNT-pathway have been identified as the main cause of the syndrome. Biallelic variants in ROR2 cause an autosomal recessive form of the syndrome with distinctive skeletal findings. Twenty-two patients with a clinical diagnosis of autosomal recessive Robinow syndrome were screened for variants in ROR2 using multiple molecular approaches. We identified 25 putatively pathogenic ROR2 variants, 16 novel, including single nucleotide variants and exonic deletions. Detailed phenotypic analyses revealed that all subjects presented with a prominent forehead, hypertelorism, short nose, abnormality of the nasal tip, brachydactyly, mesomelic limb shortening, short stature, and genital hypoplasia in male patients. A total of 19 clinical features were present in more than 75% of the subjects, thus pointing to an overall uniformity of the phenotype. Disease-causing variants in ROR2, contribute to a clinically recognizable autosomal recessive trait phenotype with multiple skeletal defects. A comprehensive quantitative clinical evaluation of this cohort delineated the phenotypic spectrum of ROR2-related Robinow syndrome. The identification of exonic deletion variant alleles further supports the contention of a loss-of-function mechanism in the etiology of the syndrome.

Impact of achondroplasia on Latin American patients: a systematic review and meta-analysis of observational studies.

BACKGROUND: Achondroplasia (ACH), the most common form of disproportionate short stature, is caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene. Recent advances in drug therapy for ACH have highlighted the importance of elucidating the natural history and socioeconomic burden of this condition. Recognition that there are many potential issues for the patient with ACH is the first step in planning cost-effective interventions in Latin America (LATAM), a vast geographic territory comprising countries with multicultural characteristics and wide socioeconomic differences. We conducted a systematic literature review to characterize the impact of ACH on affected individuals and on healthcare resources in LATAM countries. METHODS: Searches of the global medical literature as well as regional and local medical literature up to August 2020. Observational studies on patients with ACH from any LATAM country. Pairs of reviewers independently screened eligible articles, extracted data from included studies, and assessed their risk of bias. RESULTS: Fifty-three unique studies (28 case series and cross-sectional studies and 25 case reports) including data on 1604 patients were eligible. Of these studies, 11 had data available for meta-analysis. Both premature mortality and all-cause mortality in the pooled studies was 15% [95% Confidence Interval (CI) 1.0E-3 to 0.47; I2 = 82.9%, p = 0.0029; three studies, n = 99 patients]. Frequency of cardio-respiratory-metabolic disorders was 17% [95% CI 0.04-0.37; I2 = 90.3%, p < 0.0001; four studies, n = 230 patients]; nervous system disorders was 18% [95% CI 0.07-0.33; I2 = 84.6%, p < 0.0001; six studies, n = 262 patients]; ear, nose, throat and speech disorders was 32% [95% CI 0.18-0.48; I2 = 73.4%, p = 0.0046; five studies, n = 183 patients]; and spinal issues including stenosis, compression and associated pain was 24% [95% CI 0.07-0.47; I2 = 91.3%, p < 0.0001; five studies, n = 235 patients]. CONCLUSIONS: There is currently evidence of high clinical burden in ACH patients in LATAM countries. Establishing the impact of ACH provides the necessary foundation for planning tailored and effective public health interventions.

Childhood Hypophosphatasia Associated with a Novel Biallelic ALPL Variant at the TNSALP Dimer Interface.

The goal of this study was to perform a clinical and molecular investigation in an eight-year-old female child diagnosed with hypophosphatasia (HPP). The proband and her family were evaluated by medical and dental histories, biochemical analyses, radiographic imaging, and genetic analysis of the tissue-nonspecific alkaline phosphatase (ALPL) gene. A bioinformatic analysis was performed to predict the structural and functional impact of the point mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) molecule and to define their potential contribution to the phenotype. We identified a novel combination of heterozygous ALPL missense variants in the proband, p.Ala33Val and p.Asn47His, compatible with an autosomal recessive mode of inheritance and resulting in skeletal and dental phenotypes. Computational modeling showed that the affected Asn47 residue is located in the coil structure close to the N-terminal α-helix, whereas the affected Ala33 residue is localized in the N-terminal α-helix. Both affected residues are located close to the homodimer interface, suggesting they may impair TNSALP dimer formation and stability. Clinical and biochemical follow-up revealed improvements after six years of ERT. Reporting this novel combination of ALPL variants in childhood HPP provides new insights into genotype-phenotype associations for HPP and specific sites within the TNSALP molecule potentially related to a childhood-onset HPP and skeletal and dental manifestations. Beneficial effects of ERT are implicated in skeletal and dental tissues.

Targeted massively parallel sequencing for congenital generalized lipodystrophy.

OBJECTIVE: Our aim is to establish genetic diagnosis of congenital generalized lipodystrophy (CGL) using targeted massively parallel sequencing (MPS), also known as next-generation sequencing (NGS). METHODS: Nine unrelated individuals with a clinical diagnosis of CGL were recruited. We used a customized panel to capture genes related to genetic lipodystrophies. DNA libraries were generated, sequenced using the Illumina MiSeq, and bioinformatics analysis was performed. RESULTS: An accurate genetic diagnosis was stated for all nine patients. Four had pathogenic variants in AGPAT2 and three in BSCL2. Three large homozygous deletions in AGPAT2 were identified by copy-number variant analysis. CONCLUSION: Although we have found allelic variants in only 2 genes related to CGL, the panel was able to identify different variants including deletions that would have been missed by Sanger sequencing. We believe that MPS is a valuable tool for the genetic diagnosis of multi-genes related diseases, including CGL.

Long-term impact of early initiation of enzyme replacement therapy in 34 MPS VI patients: A resurvey study.

Patients with mucopolysaccharidosis type VI (MPS VI) present with a wide range of disease severity and clinical manifestations, with significant functional impairment and shortened lifespan. Enzyme replacement therapy (ERT) with galsulfase has been shown to improve clinical and biochemical parameters including patient survival, quality of life and growth. The present study is a resurvey of 34 Brazilian MPS VI patients with rapidly progressive disease (classical phenotype) who initiated ERT with galsulfase under five years of age and had been on ERT until data collection in 2019, with few exceptions (n = 4 patients who died before 2019). Anthropometric measures, urinary glycosaminoglycans, and data regarding cardiac, orthopedic, neurologic, sleep apnea, hearing and ophthalmologic outcomes were filled in by specialists. Pubertal development, clinical complications, hospitalizations, and surgeries were also assessed. In this resurvey study, treatment with galsulfase has shown to be safe and well tolerated in MPS VI patients who initiated ERT under the age of 5 years and who have been undergoing ERT for approximately 10 years. Mortality rate suggests that early initiation of ERT may have a positive impact on patients' survival, improving but not preventing disease progression and death. MPS VI patients on ERT also showed improved growth velocity and the pubertal development was normal in all surviving patients. Follow-up data on pneumonia and hospitalization suggest that early ERT may have a protective effect against major respiratory complications. Cardiac valve disease progressed since their prior evaluation and spinal cord compression was observed in a large number of patients, suggesting that these disease complications were not modified by ERT.

Phenotype-genotype analysis of 242 individuals with RASopathies: 18-year experience of a tertiary center in Brazil.

We report the clinical and molecular data of a large cohort comprising 242 individuals with RASopathies, from a single Tertiary Center in Brazil, the largest study from Latin America. Noonan syndrome represented 76% of the subjects, with heterozygous variants in nine different genes, mainly PTPN11, SOS1, RAF1, LZTR1, and RIT1, detected by Sanger and next-generation sequencing. The latter was applied to 126 individuals, with a positive yield of 63% in genes of the RAS/MAPK cascade. We present evidence that there are some allelic differences in PTPN11 across distinct populations. We highlight the clinical aspects that pose more medical concerns, such as the cardiac anomalies, bleeding diathesis and proliferative lesions. The genotype-phenotype analysis between the RASopathies showed statistically significant differences in some cardinal features, such as craniofacial and cardiac anomalies, the latter also statistically significant for different genes in Noonan syndrome. We present two individuals with a Noonan syndrome phenotype, one with an atypical, structural cardiac defect, harboring variants in genes mainly associated with isolated hypertrophic cardiomyopathy and discuss the role of these variants in their phenotype.

Lymphoproliferative disorder with polyautoimmunity and hypogammaglobulinemia: An unusual presentation of 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11.2DS) has a heterogeneous presentation that includes multiple congenital anomalies and immunodeficiency, one of the most striking features. Usually, it is characterized by T cell lymphopenia, B cell dysfunction and autoimmunity. Here, we describe an unusual case of 22q11.2DS in a patient with lymphoproliferative disorder, polyautoimmunity and hypogammaglobulinemia.

Gene expression profile suggesting immunological dysregulation in two Brazilian Bloom's syndrome cases.

BACKGROUND: Bloom syndrome (BS) is a rare autosomal recessive chromosome instability disorder. The main clinical manifestations are growth deficiency, telangiectasic facial erythema, immunodeficiency, and increased risk to develop neoplasias at early age. Cytogenetic test for sister chromatid exchanges (SCEs) is used as a diagnostic marker for BS. In addition, most patients also present mutations in the BLM gene, related to defects in the DNA repair mechanism. However, the molecular mechanism behind the pathogenicity of BS is still not completely understood. METHODS: We describe two patients confirmed with BS by SCE and molecular analysis. Also, we performed the gene expression profile by the RNA-seq methodology in mRNA transcripts for differential gene expression analysis using as a biological condition for comparison BS versus health controls. RESULTS: We detected 216 differentially expressed genes related to immunological pathways such as positive regulation and activation of B cells, immune effector process and absence of difference of DNA repair genes expression. In addition; we also observed differentially expressed genes associated with apoptosis control, such as BCL2L1, CASP7, CDKN1A, E2F2, ITPR, CD274, TNFAIP6, TNFRSF25, TNFRSF13C, and TNFRSF17. CONCLUSION: Our results suggest that the combination of altered expression of genes involved in signaling pathways of immune response and apoptosis control may contribute directly to the main characteristics observed in BS, such as recurrent infections, growth failure, and high risk of cancer. Transcriptome studies of other instability syndromes could allow a more accurate analysis of the relevant gene interactions associated with the destabilization of the genome. This is a first description of the profile of differential gene expression related to immunological aspects detected in patients with BS by RNA-seq.

Loss of TNR causes a nonprogressive neurodevelopmental disorder with spasticity and transient opisthotonus.

PURPOSE: TNR, encoding Tenascin-R, is an extracellular matrix glycoprotein involved in neurite outgrowth and neural cell adhesion, proliferation and migration, axonal guidance, myelination, and synaptic plasticity. Tenascin-R is exclusively expressed in the central nervous system with highest expression after birth. The protein is crucial in the formation of perineuronal nets that ensheath interneurons. However, the role of Tenascin-R in human pathology is largely unknown. We aimed to establish TNR as a human disease gene and unravel the associated clinical spectrum. METHODS: Exome sequencing and an online matchmaking tool were used to identify patients with biallelic variants in TNR. RESULTS: We identified 13 individuals from 8 unrelated families with biallelic variants in TNR sharing a phenotype consisting of spastic para- or tetraparesis, axial muscular hypotonia, developmental delay, and transient opisthotonus. Four homozygous loss-of-function and four different missense variants were identified. CONCLUSION: We establish TNR as a disease gene for an autosomal recessive nonprogressive neurodevelopmental disorder with spasticity and transient opisthotonus and highlight the role of central nervous system extracellular matrix proteins in the pathogenicity of spastic disorders.

Breakpoint delineation in 5p- patients leads to new insights about microcephaly and the typical high-pitched cry.

BACKGROUND: Cri du chat syndrome (CdCS) is a rare syndrome caused by a partial or complete deletion of the short arm of chromosome 5 (5p-). The main clinical features include a high-pitched cry, facial asymmetry, microcephaly, round face at birth, epicanthal folds, hypotonia, delayed growth and development. METHODS: We studied 14 Brazilian patients with CdCS using genomic array in order to better define the 5p breakpoints and recognize copy number variations (CNVs) that contribute to clinical manifestations associated with the syndrome. RESULTS: Array confirmed terminal deletions in 13 patients and an interstitial deletion in one patient. It was also possible to map the breakpoints and associate a genomic region of 4.7 Mb to the development of head circumference and cat-like cry. We also found other CNVs concomitant to the 5p deletion including a 9p duplication, a 17q deletion, and a 22q deletion in three different patients. CONCLUSION: With advancements of molecular cytogenomic methods in the last two decades, it was possible to evidence cryptic alterations and improve the genotype-phenotype correlation. In this work, we describe a new genomic region associated with microcephaly and cat-like cry and highlight the importance of precise delineation of 5p deletion breakpoints and detection of other CNVs in CdCS patients to improve genotype-phenotype correlation to perform a complete clinical and molecular diagnosis.

Growth and Clinical Characteristics of Children with Floating-Harbor Syndrome: Analysis of Current Original Data and a Review of the Literature.

BACKGROUND: Floating-Harbor syndrome (FHS) is a rare condition characterized by dysmorphic facial features, short stature, and expressive language delay. OBJECTIVE: The aim of this study was to describe a cohort of patients with FHS and review the literature about the response to recombinant human growth hormone (rhGH) therapy. METHODS: Anthropometric and laboratory data from 7 patients with FHS were described. The molecular diagnosis was established by multigene analysis. Moreover, we reviewed the literature concerning patients with FHS treated with rhGH. RESULTS: All 7 patients were born small for gestational age. At first evaluation, 6 patients had a height standard deviation score (SDS) ≤-2 and 1 had short stature in relation to their target height. Bone age was usually delayed, which rapidly advanced during puberty. Nonspecific skeletal abnormalities were frequently noticed, and normal to elevated plasma IGF-I levels were observed in all except 1 patient with growth hormone deficiency. Information about 20 patients with FHS treated with rhGH was analyzed (4 from our cohort and 16 from the literature). The median height changes during the treatment period (approx. 2.9 years) were 1.1 SDS (range from -0.4 to 3.1). Nontreated patients had an adult height SDS of -4.1 ± 1.2 (n = 10) versus -2.6 ± 0.8 SDS (n = 7, p 0.012) for treated patients. CONCLUSION: We observed a laboratory profile compatible with IGF-1 insensitivity in some patients with FHS. Nevertheless, our study suggests that children with FHS may be considered as candidates for rhGH therapy. Further studies are necessary to establish the real benefit and safety of rhGH therapy in these patients.

Primary immunodeficiency with chronic enteropathy and developmental delay in a boy arising from a novel homozygous RIPK1 variant.

Identification of genetic causes of primary monogenic immunodeficiencies would strengthen the current understanding of their immunopathology. Pathogenic variants in genes in association with tumor necrosis factor α (TNFα) signaling, including OTULIN, TNFAIP3, RBCK1, and RNF31 cause human congenital autoinflammatory diseases with/without immunodeficiency. RIPK1, encoding a receptor interacting serine/threonine kinase 1, is present in protein complexes mediating signal transduction including TNF receptor 1. Biallelic loss-of-function variants in RIPK1 were recently reported in individuals with primary immunodeficiency with intestinal bowel disease and arthritis. Here, we report a novel homozygous RIPK1 variant in a boy with immunodeficiency and chronic enteropathy. Our patient exhibited severe motor delay and mild intellectual disability, which were previously unknown. The present results are expected to deepen the current understanding of clinical features based on RIPK1 abnormalities.

Impact of Growth Hormone Therapy on Adult Height in Patients with PTPN11 Mutations Related to Noonan Syndrome.

OBJECTIVES: The aim of this study was to evaluate the response to recombinant human growth hormone (rhGH) treatment in patients with Noonan syndrome (NS). MATERIALS AND METHODS: Forty-two patients (35 PTPN11+) were treated with rhGH, and 17 were followed-up until adult height. The outcomes were changes in growth velocity (GV) and height standard deviation scores (SDS) for normal (height-CDC SDS) and Noonan standards (height-NS SDS). RESULTS: The pretreatment chronological age was 10.3 ± 3.5 years. Height-CDC SDS and height-NS SDS were -3.1 ± 0.7 and -0.5 ± 0.6, respectively. PTPN11+ patients had a better growth response than PTPN11- patients. GV SDS increased from -1.2 ± 1.8 to 3.1 ± 2.8 after the first year of therapy in PTPN11+ patients, and from -1.9 ± 2.6 to -0.1 ± 2.6 in PTPN11- patients. The gain in height-CDC SDS during the first year was higher in PTPN11+ than PTPN11- (0.6 ± 0.4 vs. 0.1 ± 0.2, p = 0.008). Similarly, the gain was observed in height-NS SDS (0.6 ± 0.3 vs. 0.2 ± 0.2, respectively, p < 0.001). Among the patients that reached adult height (n = 17), AH-CDC SDS and AH-NS SDS were -2.1 ± 0.7 and 0.7 ± 0.8, respectively. The total increase in height SDS was 1.3 ± 0.7 and 1.5 ± 0.6 for normal and NS standards, respectively. CONCLUSIONS: This study supports the advantage of rhGH therapy on adult height in PTPN11+ patients. In comparison, PTPN11- patients showed a poor response to rhGH. However, this PTPN11- group was small, preventing an adequate comparison among different genotypes and no guarantee of response to therapy in genes besides PTPN11.

Mosaic Trisomy 12 Associated with Overgrowth Detected in Fibroblast Cell Lines.

Mosaic trisomy 12 is a rare anomaly, and only 9 cases of live births with this condition have been reported in the literature. The clinical phenotype is variable, including neuropsychomotor developmental delay, congenital heart disease, microcephaly, cutaneous spots, facial asymmetry, prominent ears, hypotonia, retinopathy, and sensorineural hearing loss. A 2-year-old female presented with neuropsychomotor developmental delay, prominent forehead, dolichocephaly, patchy skin pigmentation, and unexpected overgrowth at birth. Cytogenetic analysis of her peripheral blood showed normal results, suggesting the presence of a chromosomal alteration in other tissues. Further studies using G-banding and FISH performed on fibroblasts from both hyper- and hypopigmented regions identified a 47,XX,+12/46,XX karyotype. To the best of our knowledge, no patients with mosaic trisomy 12 associated with overgrowth have been reported to date. Congenital overgrowth and neonatal overgrowth have been frequently linked to Pallister-Killian syndrome (PKS; OMIM 601803). This case suggests the possibility of an association of genes present in the 12p region with fetal overgrowth, considering that chromosomal duplications could lead to an increase in the production of aberrant transcripts and disturbing gene dosage effects. This case highlights the importance of cytogenetic analysis in different tissues to provide relevant information to the specific genotype/phenotype correlation.

Novel fibronectin mutations and expansion of the phenotype in spondylometaphyseal dysplasia with "corner fractures".

Heterozygous pathogenic variants in the FN1 gene, encoding fibronectin (FN), have recently been shown to be associated with a skeletal disorder in some individuals affected by spondylometaphyseal dysplasia with "corner fractures" (SMD-CF). The most striking feature characterizing SMD-CF is irregularly shaped metaphyses giving the appearance of "corner fractures". An array of secondary features, including developmental coxa vara, ovoid vertebral bodies and severe scoliosis, may also be present. FN is an important extracellular matrix component for bone and cartilage development. Here we report five patients affected by this subtype of SMD-CF caused by five novel FN1 missense mutations: p.Cys123Tyr, p.Cys169Tyr, p.Cys213Tyr, p.Cys231Trp and p.Cys258Tyr. All individuals shared a substitution of a cysteine residue, disrupting disulfide bonds in the FN type-I assembly domains located in the N-terminal assembly region. The abnormal metaphyseal ossification and "corner fracture" appearances were the most remarkable clinical feature in these patients. In addition, generalized skeletal fragility with low-trauma bilateral femoral fractures was identified in one patient. Interestingly, the distal femoral changes in this patient healed with skeletal maturation. Our report expands the phenotypic and genetic spectrum of the FN1-related SMD-CF and emphasizes the importance of FN in bone formation and possibly also in the maintenance of bone strength.

Large deletion in PIGL: a common mutational mechanism in CHIME syndrome?

Abstract CHIME syndrome is an extremely rare autosomal recessive multisystemic disorder caused by mutations in PIGL. PIGL is an endoplasmic reticulum localized enzyme that catalyzes the second step of glycosylphosphatidylinositol (GPI) biosynthesis, which plays a role in the anchorage of cell-surface proteins including receptors, enzymes, and adhesion molecules. Germline mutations in other members of GPI and Post GPI Attachment to Proteins (PGAP) family genes have been described and constitute a group of diseases within the congenital disorders of glycosylation. Patients in this group often present alkaline phosphatase serum levels abnormalities and neurological symptoms. We report a CHIME syndrome patient who harbors a missense mutation c.500T > C (p.Leu167Pro) and a large deletion involving the 5' untranslated region and part of exon 1 of PIGL. In CHIME syndrome, a recurrent missense mutation c.500T > C (p.Leu167Pro) is found in the majority of patients, associated with a null mutation in the other allele, including an overrepresentation of large deletions. The latter are not detected by the standard analysis in sequencing techniques, including next-generation sequencing. Thus, in individuals with a clinical diagnosis of CHIME syndrome in which only one mutation is found, an active search for a large deletion should be sought.

Large deletion in PIGL: a common mutational mechanism in CHIME syndrome?

CHIME syndrome is an extremely rare autosomal recessive multisystemic disorder caused by mutations in PIGL. PIGL is an endoplasmic reticulum localized enzyme that catalyzes the second step of glycosylphosphatidylinositol (GPI) biosynthesis, which plays a role in the anchorage of cell-surface proteins including receptors, enzymes, and adhesion molecules. Germline mutations in other members of GPI and Post GPI Attachment to Proteins (PGAP) family genes have been described and constitute a group of diseases within the congenital disorders of glycosylation. Patients in this group often present alkaline phosphatase serum levels abnormalities and neurological symptoms. We report a CHIME syndrome patient who harbors a missense mutation c.500T > C (p.Leu167Pro) and a large deletion involving the 5' untranslated region and part of exon 1 of PIGL. In CHIME syndrome, a recurrent missense mutation c.500T > C (p.Leu167Pro) is found in the majority of patients, associated with a null mutation in the other allele, including an overrepresentation of large deletions. The latter are not detected by the standard analysis in sequencing techniques, including next-generation sequencing. Thus, in individuals with a clinical diagnosis of CHIME syndrome in which only one mutation is found, an active search for a large deletion should be sought.

CBS mutations are good predictors for B6-responsiveness: A study based on the analysis of 35 Brazilian Classical Homocystinuria patients.

BACKGROUND: Classical homocystinuria (HCU) is a monogenic disease caused by the deficient activity of cystathionine ß-synthase (CßS). The objective of this study was to identify the CBS mutations in Brazilian patients with HCU. METHODS: gDNA samples were obtained for 35 patients (30 families) with biochemically confirmed diagnosis of HCU. All exons and exon-intron boundaries of CBS gene were sequenced. Gene expression analysis by qRT-PCR was performed in six patients. Novel missense point mutations were expressed in E. coli by site-directed mutagenesis. RESULTS: Parental consanguinity was reported in 16 families, and pyridoxine responsiveness in five (15%) patients. Among individuals from the same family, all presented the same phenotype. Both pathogenic mutations were identified in 29/30 patients. Twenty-one different mutations were detected in nine exons and three introns; being six common mutations. Most prevalent were p.Ile278Thr (18.2%), p.Trp323Ter (11.3%), p.Thr191Met (11.3%), and c.828+1G>A (11.3%). Eight novel mutations were found [c.2T>C, c.209+1delG, c.284T>C, c.329A>T, c.444delG, c.864_868delGAG c.989_991delAGG, and c.1223+5G>T]. Enzyme activity in E. coli-expressed mutations was 1.5% for c.329A>T and 17.5% for c.284T>C. qRT-PCR analysis revealed reduced gene expression in all evaluated genotypes: [c.209+1delG; c.572C>T]; [c.2T>C; c.828+1G>A]; [c.828+1G>A; c.1126G>A]; [c.833T>C; c.989_991delAGG]; [c.1058C>T; c.146C>T]; and [c.444delG; c.444delG]. The expected phenotype according to the genotype (pyridoxine responsiveness) matched in all cases. CONCLUSIONS: Most patients studied were pyridoxine nonresponsive and presented early manifestations, suggesting severe phenotypes. Many private mutations were observed, but the four most prevalent mutations together accounted for over 50% of mutated alleles. A good genotype-phenotype relationship was observed within families and for the four most common mutations.

Recurrent Copy Number Variants Associated with Syndromic Short Stature of Unknown Cause.

BACKGROUND/AIMS: Genetic imbalances are responsible for many cases of short stature of unknown etiology. This study aims to identify recurrent pathogenic copy number variants (CNVs) in patients with syndromic short stature of unknown cause. METHODS: We selected 229 children with short stature and dysmorphic features, developmental delay, and/or intellectual disability, but without a recognized syndrome. All patients were evaluated by chromosomal microarray (array-based comparative genomic hybridization/single nucleotide polymorphism array). Additionally, we searched databases and previous studies to recover recurrent pathogenic CNVs associated with short stature. RESULTS: We identified 32 pathogenic/probably pathogenic CNVs in 229 patients. By reviewing the literature, we selected 4 previous studies which evaluated CNVs in cohorts of patients with short stature. Taken together, there were 671 patients with short stature of unknown cause evaluated by chromosomal microarray. Pathogenic/probably pathogenic CNVs were identified in 87 patients (13%). Seven recurrent CNVs, 22q11.21, 15q26, 1p36.33, Xp22.33, 17p13.3, 1q21.1, 2q24.2, were observed. They are responsible for about 40% of all pathogenic/probably pathogenic genomic imbalances found in short stature patients of unknown cause. CONCLUSION: CNVs seem to play a significant role in patients with short stature. Chromosomal microarray should be used as a diagnostic tool for evaluation of growth disorders, especially for syndromic short stature of unknown cause.