Diagnostic accuracy and the first genotype-phenotype correlation in glycogen storage disease type V.

BACKGROUND: Glycogen storage disease type V (GSDV) is an autosomal recessive metabolic condition caused by pathogenic PYGM variants. This is an underdiagnosed condition as it presents with exercise intolerance in children. We reviewed the GSDV cases of a tertiary hospital center to assess diagnostic timing/accuracy, as well as potential clinical/analytical predictors of such factors. METHODS: We retrospectively reviewed all GSDV cases with follow-up in both Pediatric and Adult Metabolic Diseases consultations. We included 28 cases and assessed their hospital record for clinical information. RESULTS: Over 90% of our cases had late diagnoses, with more than 50% being diagnosed in adulthood despite symptom onset in preschool (very late diagnosis). Diagnostic age was lower in patients exhibiting myoglobinuria. Interestingly, patients with a positive family history of GSDV had similar rates of very late diagnoses, likely since the index case was already detected very late in life. Finally, we observe that the R50* variant is associated with increased myoglobinuria and CK elevation, in a dosage-dependent manner. CONCLUSION: We concluded that GSDV is severely underdiagnosed, and that some clinical and analytical aspects of the condition can be more indicative of this diagnosis. Furthermore, we propose for the first time a genotype-phenotype correlation in GSDV. IMPACT: GSDV is a pediatric-onset metabolic disorder that is mostly diagnosed late in the adult age and commonly misdiagnosed. We observed the first genotype-phenotype correlation in GSDV, regarding the common R50* variant. Awareness of GSDV for pediatricians and the overall medical community is vital.

Pre-implantation Genetic Testing in Inherited Metabolic Diseases? Stateof- the-art and current challenges.

INTRODUCTION: Inborn errors of metabolism (IEM) are genetic diseases involving congenital disorders of enzyme activities. Most follow Mendelian autosomal recessive inheritance and few follow mitochondrial inheritance. In many cases, after the birth of an affected child parents discover that have been the carriers for the condition and worry about the risk of recurrence in future offspring. Preimplantation genetic testing (PGT) can analyze embryos before their transfer to the uterus and prevent the transmission of hereditary conditions to descendants, however this procedure is of limited value in mtDNA conditions. METHODS: The list of diseases currently approved for PGT were reviewed. The process for eligibility, was as for the Comissão Nacional Procriação Medicamente Assistida (CNPMA), of Portugal (PT). Review of international practices for Assisted Reproductive Techniques (ART) in IEM was carried out. RESULTS: As of 07.2022, 23 IEM diseases associated with deleterious variants in nDNA were approved for PGT in PT. Couples at risk for conditions not included in the list can solicit an evaluation from an expert committee, after a medical genetics consultation. To qualify for approval, diseases must cause significant suffering and/or premature death. Due to a greater number of solicitations many more IEM conditions have been approved for PGT across the world. ART for mtDNA is not available in PT. International expert centers include PGT for specific well documented variants and mitochondrial donation. CONCLUSION: PGT is a reliable approach to reduce the risk of transmission of a genetic condition to the offspring. The list of IEM disorders currently accepted for this technique in Portugal are small, but it is expanding, as many more diseases fit the necessary criteria. While appealing in theory, low success rates coupled with limited availability can be discouraging for patients. Genetic counselling is of paramount importance after the diagnosis of IEM diseases. It is important for both clinicians and patients to be made aware of the available reproductive options and their limitations.

An SPG7 mutation as a novel cause of monogenic progressive muscular atrophy.

BACKGROUND: Progressive muscular atrophy (PMA) is a rare adult-onset neurological disease that is characterized by isolated lower motor neuron degeneration. While it is still disputable whether PMA is a subtype of amyotrophic lateral sclerosis (ALS) or an isolated disorder, it is well-established as a clinically defined entity. About 5% of PMA cases are monogenic, and the implicated genes largely overlap with those causing monogenic ALS. CASE DESCRIPTION: Here we describe a 68-year-old female patient with progressive and asymmetric upper-limb weakness throughout an 18-month period, with muscle atrophy, dysphagia and slurring of speech. The lower limbs were unaffected, and there was no sign of upper motor neuron dysfunction. Comprehensive genetic testing for single nucleotide and copy-number variants revealed a pathogenic monoallelic variant c.1529C>T, p.(Ala510Val) in the SPG7 gene. DISCUSSION: Pathogenic biallelic SPG7 variants have been originally associated with hereditary spastic paraplegia, but other phenotypes are nowadays known to be linked to these variants, such as ALS. However, there is no report of this (or any) other SPG7 variant in association with PMA, whether it progressed to ALS or not. In conclusion, we present the first known case of PMA associated with a monoallelic SPG7 mutation.

Predicting factors of neurodevelopmental performance in children with phenylketonuria.

In phenylketonuria (PKU), high phenylalanine (Phe) levels hamper neurodevelopment impairing executive function later in life. While the second has been more studied, fewer data exist on predictors of PKU patients' development in specific populations. To contribute to the field, we performed a retrospective analysis of predictors of neurodevelopment in PKU patients in a Portuguese cohort. We analyzed the retrospective data on the metabolic control of 89 patients, as their health and familial features. Griffith's Mental Development Scale performance at age 6 (GMDS6) was used to assess neurodevelopment. Our cohort included 14 GMDS6low and 75 GMDS6high patients. In a multivariate analysis, the better predictors of neurodevelopment were the metabolic control at age 3 and year of birth (n = 87, ß0  = -121, ß1  = -1.77, ß2  = 0.06, LRchi2(2) = 13.61, Prob > chi2 = 0.001, Pseudo R2 = 0.1773). With this model, it was possible to define a safety cut-off of 7.8 mg/dL for the Phe level at age 3 (sensitivity = 72.6%, specificity = 78.6%), confirming the safety of the cut-off of 6 mg/dL already used in the clinical practice. Our study supports the relevance of metabolic control to predict the neurodevelopment of PKU patients, in the historical context of the disease management.

Genetic counseling and carrier screening in candidates for gamete donation at a Portuguese center.

OBJECTIVE: Genetic counseling and carrier screening are part of the gamete donation process by healthy individuals. We aim to review the findings of genetic counseling and carrier screening of a cohort of candidates at our public gametes bank. METHODS: Thirty-four male and 64 female candidates had genetic counseling with a medical geneticist before donation. Of these, one female candidate voluntarily dropped-out. Thirty-four males and 63 females performed karyotype and screening for the more common pathogenic variants for CFTR-related cystic fibrosis and spinal muscular atrophy (SMN1) in the Portuguese population. In addition, all females also performed Fragile X expansion screening (FMR1). Thirty candidates with known or assumed African ancestry performed hemoglobinopathies screening. RESULTS: Six candidates were definitely or temporarily withheld from the donation process given their family or personal history that required further investigation. Of 97 candidates tested, 16.5% presented anomalous laboratory results (16/97): ten candidates were carriers for an autosomal recessive disorder - cystic fibrosis (5/97), sickle cell anemia (3/30), and spinal muscular atrophy (2/97). One female was an FMR1 pre-mutation carrier (1/63). One female candidate presented with triple X mosaicism: 47,XXX[2]/46,XX[50]. Two candidates presented with chromosomal instability of unknown origin. In one candidate, a mosaic for the Philadelphia chromosome was detected, revealing the diagnosis of chronic myeloid leukemia. CONCLUSIONS: From a cohort of 97 candidates, 21.7% had a family/personal history or an anomalous laboratory result that required additional genetic counseling, stressing the importance of performing pre-donation genetic counseling in this population.

Refining the Clinical Spectrum of the 17p13.3 Microduplication Syndrome: Case-Report of a Familial Small Microduplication.

The chromosomal region 17p13.3 contains extensive repetitive sequences and is a well-recognized region of genomic instability. The 17p13.3 microduplication syndrome has been associated with a clinical spectrum of moderately non-specific phenotypes, including global developmental delay/intellectual disability, behavioral disorders, autism spectrum disorder and variable dysmorphic features. Depending on the genes involved in the microduplication, it can be categorized in two subtypes with different phenotypes. Here, we report a case of a 7-year-old boy with global developmental delay, speech impairment, hypotonia, behavioral conditions (ADHD and ODD), non-specific dysmorphic features and overgrowth. Genetic testing revealed a small 17p13.3 chromosomal duplication, which included the BHLHA9, CRK and YWHAE genes. Additionally, we observed that this was maternally inherited, and that the mother presented with a milder phenotype including mild learning disabilities, speech impairment and non-specific dysmorphic features, which did not significantly affect her. In conclusion, we present a clinical case of a 17p13.3 duplication that further delineates the clinical spectrum of this syndrome, including its intrafamilial/intergenerational variability.

A new tool to screen patients with severe obstructive sleep apnea in the primary care setting: a prospective multicenter study.

BACKGROUND: The coordination between different levels of care is essential for the management of obstructive sleep apnea (OSA). The objective of this multicenter project was to develop a screening model for OSA in the primary care setting. METHODS: Anthropometric data, clinical history, and symptoms of OSA were recorded in randomly selected primary care patients, who also underwent a home sleep apnea test (HSAT). Respiratory polygraphy or polysomnography were performed at the sleep unit to establish definite indication for continuous positive airway pressure (CPAP). By means of cross-validation, a logistic regression model (CPAP yes/no) was designed, and with the clinical variables included in the model, a scoring system was established using the ß coefficients (PASHOS Test). In a second stage, results of HSAT were added, and the final accuracy of the model was assessed. RESULTS: 194 patients completed the study. The clinical test included the body mass index, neck circumference and observed apneas during sleep (AUC 0.824, 95% CI 0.763-0.886, P < 0.001). In a second stage, the oxygen desaturation index (ODI) of 3% (ODI3% ≥ 15%) from the HSAT was added (AUC 0.911, 95% CI 0.863-0.960, P < 0.001), with a sensitivity of 85.5% (95% CI 74.7-92.1) and specificity of 67.8% (95% CI 55.1-78.3). CONCLUSIONS: The use of this model would prevent referral to the sleep unit for 55.1% of the patients. The two-stage PASHOS model is a useful and practical screening tool for OSA in primary care for detecting candidates for CPAP treatment. Clinical Trial Registration Registry: ClinicalTrials.gov; Name: PASHOS Project: Advanced Platform for Sleep Apnea Syndrome Assessment; URL: https://clinicaltrials.gov/ct2/show/NCT02591979 ; Identifier: NCT02591979. Date of registration: October 30, 2015.

Impaired catabolism of free oligosaccharides due to MAN2C1 variants causes a neurodevelopmental disorder.

Free oligosaccharides (fOSs) are soluble oligosaccharide species generated during N-glycosylation of proteins. Although little is known about fOS metabolism, the recent identification of NGLY1 deficiency, a congenital disorder of deglycosylation (CDDG) caused by loss of function of an enzyme involved in fOS metabolism, has elicited increased interest in fOS processing. The catabolism of fOSs has been linked to the activity of a specific cytosolic mannosidase, MAN2C1, which cleaves α1,2-, α1,3-, and α1,6-mannose residues. In this study, we report the clinical, biochemical, and molecular features of six individuals, including two fetuses, with bi-allelic pathogenic variants in MAN2C1; the individuals are from four different families. These individuals exhibit dysmorphic facial features, congenital anomalies such as tongue hamartoma, variable degrees of intellectual disability, and brain anomalies including polymicrogyria, interhemispheric cysts, hypothalamic hamartoma, callosal anomalies, and hypoplasia of brainstem and cerebellar vermis. Complementation experiments with isogenic MAN2C1-KO HAP1 cells confirm the pathogenicity of three of the identified MAN2C1 variants. We further demonstrate that MAN2C1 variants lead to accumulation and delay in the processing of fOSs in proband-derived cells. These results emphasize the involvement of MAN2C1 in human neurodevelopmental disease and the importance of fOS catabolism.

A Novel Frameshift CHD4 Variant Leading to Sifrim-Hitz-Weiss Syndrome in a Proband with a Subclinical Familial t(17;19) and a Large dup(2)(q14.3q21.1).

The genetic complexity of neurodevelopmental disorders (NDD), combined with a heterogeneous clinical presentation, makes accurate assessment of their molecular bases and pathogenic mechanisms challenging. Our purpose is to reveal the pathogenic variant underlying a complex NDD through identification of the "full" spectrum of structural genomic and genetic variants. Therefore, clinical phenotyping and identification of variants by genome and exome sequencing, together with comprehensive assessment of these and affected candidate genes, were carried out. A maternally-inherited familial translocation [t(17;19)(p13.1;p13.3)mat] disrupting the GSG1 like 2 gene (GSG1L2), a 3.2 Mb dup(2)(q14.3q21.1) encompassing the autosomal dominant OMIM phenotype-associated PROC and HS6ST1 gene, and a novel frameshift c.4442del, p.(Gly1481Valfs*21) variant within exon 30 of the Chromodomain helicase DNA binding protein 4 (CHD4) have been identified. Considering the pathogenic potential of each variant and the proband's phenotype, we conclude that this case basically fits the Sifrim-Hitz-Weiss syndrome or CHD4-associated neurodevelopmental phenotype. Finally, our data highlight the need for identification of the "full" spectrum of structural genomic and genetic variants and of reverse comparative phenotyping, including unrelated patients with variants in same genes, for improved genomic healthcare of patients with NDD.

Congenital Disorders of Glycosylation in Portugal-Two Decades of Experience.

OBJECTIVE: To describe the clinical, biochemical, and genetic features of both new and previously reported patients with congenital disorders of glycosylation (CDGs) diagnosed in Portugal over the last 20 years. STUDY DESIGN: The cohort includes patients with an unexplained multisystem or single organ involvement, with or without psychomotor disability. Serum sialotransferrin isoforms and, whenever necessary, apolipoprotein CIII isoforms and glycan structures were analyzed. Additional studies included measurement of phosphomannomutase (PMM) activity and analysis of lipid-linked oligosaccharides in fibroblasts. Sanger sequencing and massive parallel sequencing were used to identify causal variants or the affected gene, respectively. RESULTS: Sixty-three individuals were diagnosed covering 14 distinct CDGs; 43 patients diagnosed postnatally revealed a type 1, 14 a type 2, and 2 a normal pattern on serum transferrin isoelectrofocusing. The latter patients were identified by whole exome sequencing. Nine of them presented also a hypoglycosylation pattern on apolipoprotein CIII isoelectrofocusing, pointing to an associated O-glycosylation defect. Most of the patients (62%) are PMM2-CDG and the remaining carry pathogenic variants in ALG1, ATP6AP1, ATP6AP2, ATP6V0A2, CCDC115, COG1, COG4, DPAGT1, MAN1B1, SLC35A2, SRD5A3, RFT1, or PGM1. CONCLUSIONS: Portuguese patients with CDGs are presented in this report, some of them showing unique clinical phenotypes. Among the 14 genes mutated in Portuguese individuals, 8 are shared with a previously reported Spanish cohort. However, regarding the mutational spectrum of PMM2-CDG, the most frequent CDG, a striking similarity between the 2 populations was found, as only 1 mutated allele found in the Portuguese group has not been reported in Spain.

Usher syndrome and Nebulin-associated myopathy in a single patient due to variants in MYO7A and NEB.

In a patient with Usher syndrome and atypical muscle complaints, we have identified two separate variants in MYO7A andNEB genes by exome sequencing. The homozygous variants in these two recessive genes could explain the full phenotype of our patient.

Hyperinsulinaemic Hypoglycaemia and Polycystic Kidney Disease - A Rare Case Concerning PMM2 Gene Pleiotropy.

Co-occurrence of hyperinsulinaemic hypoglycaemia and polycystic kidney disease (HIPKD) has been recently described. It is caused by a non-coding variant in the promoter region for phosphomannomutase 2 (PMM2), c.-167G>T, both in homozygous or compound heterozygous variants with deleterious coding. Although PMM2 has been associated with congenital disorder of glycosylation, patients do not present with this phenotype and have normal carbohydrate-deficient transferring testing. The authors present a rare case where specific PMM2 study was performed as a result of clinical suspicions. The patient was a 6-year-old female followed at our clinic due to congenital hyperinsulinism since she was 1 month old. She also presented with bilateral polycystic kidneys, detected in prenatal set, and simple hepatic cysts, for which she was treated with diazoxide and captopril. Initial metabolic and genetic studies were normal. PMM2 gene sequence study revealed the promotor variant c.-167G>T in compound heterozygosity with the previously described pathogenic variant c.422G>A (p.Arg141His), confirming the diagnosis of HIPKD. This is a notable case as it highlights the importance of keeping this diagnostic hypothesis in mind and serves as a reminder to perform proper clinical and genetic investigation. A correct, and early, diagnosis will avoid unnecessary additional investigations and will allow appropriate genetic counselling for this autosomal recessive disorder.

Subtelomeric Rearrangements: Presentation of 21 Probands with Emphasis on Familial Cases.

INTRODUCTION: Intellectual disability affects 2% - 3% of the general population, with a chromosomal abnormality being found in 4% - 28% of these patients and a cryptic subtelomeric abnormality in 3% - 16%. In most cases, these subtelomeric rearrangements are submicroscopic, requiring techniques other than conventional karyotype for detection. They may be de novo or inherited from an affected parent or from a healthy carrier of a balanced chromosomal abnormality. The aim of this study was to characterize patients from our medical genetics center, in whom both a deletion and duplication in subtelomeric regions were found. MATERIAL AND METHODS: Clinical and cytogenetic characterization of 21 probands followed at our center, from 1998 until 2017, with subtelomeric rearrangements. RESULTS: There were 21 probands from 19 families presenting with intellectual disability and facial dysmorphisms. Seven had behavior changes, five had epilepsy and 14 presented with some other sign or symptom. Four had chromosomal abnormalities detected by conventional karyotype and four were diagnosed by array-comparative genomic hybridization. In four cases, parental studies were not possible. The online mendelian inheritance in man classification was provided whenever any of the phenotypes (deletion or duplication syndrome) was dominant. DISCUSSION: Patients and relevant family members were clinically and cytogenetically characterized. Although rare, subtelomeric changes are a substantial cause of syndromic intellectual disability with important familial repercussions. It is essential to remember that a normal array-comparative genomic hybridization result does not exclude a balanced rearrangement in the parents. CONCLUSION: Parental genetic studies are essential not only for a complete characterization of the rearrangement, but also for accurate genetic counselling and screening of family members at risk for recurrence.

Introdução: O défice intelectual afeta 2% ­ 3% da população geral, sendo encontrada uma alteração cromossómica em 4% ­ 28% dos casos e uma alteração subtelomérica em 3% ­ 16%. Estas alterações subteloméricas são, na maioria dos casos, submicroscópi- cas, não sendo detetadas no cariótipo convencional. Podem ser de novo ou herdadas de um progenitor afetado ou de um progenitor saudável portador de um rearranjo equilibrado. O objetivo deste estudo foi caracterizar os doentes seguidos no nosso centro de gené- tica médica com uma deleção e uma duplicação nas regiões subteloméricas. Material e Métodos: Caracterização clínica e citogenética de 21 probandos com alterações subteloméricas seguidos no nosso centro entre 1998 e 2017. Resultados: Foram caracterizados 21 probandos que apresentavam défice intelectual e dismorfia facial, pertencentes a 19 famílias. Sete tinham alterações do comportamento, cinco epilepsia e 14 outro sinal ou sintoma. Quatro tinham alterações no cariótipo e quatro foram diagnosticados por array-comparative genomic hybridization. Em quatro famílias não foi possível o estudo dos progenitores. Quando um dos fenótipos era dominante (síndrome de deleção ou duplicação), foi atribuída a classificação online mendelian inheri- tance in man. Discussão: Foi realizada classificação dos doentes e das famílias. As alterações nas regiões subteloméricas são, apesar de raras, uma causa substancial para défice intelectual sindrómico com repercussões familiares importantes. É essencial lembrar que um array- comparative genomic hybridization normal não exclui um rearranjo equilibrado familiar. Conclusão: O estudo dos progenitores é essencial não só para caracterização completa do rearranjo mas também para um aconse- lhamento genético preciso e identificação de familiares em risco de recorrência.

Genomic imbalances defining novel intellectual disability associated loci.

BACKGROUND: High resolution genome-wide copy number analysis, routinely used in clinical diagnosis for several years, retrieves new and extremely rare copy number variations (CNVs) that provide novel candidate genes contributing to disease etiology. The aim of this work was to identify novel genetic causes of neurodevelopmental disease, inferred from CNVs detected by array comparative hybridization (aCGH), in a cohort of 325 Portuguese patients with intellectual disability (ID). RESULTS: We have detected CNVs in 30.1% of the patients, of which 5.2% corresponded to novel likely pathogenic CNVs. For these 11 rare CNVs (which encompass novel ID candidate genes), we identified those most likely to be relevant, and established genotype-phenotype correlations based on detailed clinical assessment. In the case of duplications, we performed expression analysis to assess the impact of the rearrangement. Interestingly, these novel candidate genes belong to known ID-related pathways. Within the 8% of patients with CNVs in known pathogenic loci, the majority had a clinical presentation fitting the phenotype(s) described in the literature, with a few interesting exceptions that are discussed. CONCLUSIONS: Identification of such rare CNVs (some of which reported for the first time in ID patients/families) contributes to our understanding of the etiology of ID and for the ever-improving diagnosis of this group of patients.

The contribution of 7q33 copy number variations for intellectual disability.

Copy number variations (CNVs) at the 7q33 cytoband are very rarely described in the literature, and almost all of the cases comprise large deletions affecting more than just the q33 segment. We report seven patients (two families with two siblings and their affected mother and one unrelated patient) with neurodevelopmental delay associated with CNVs in 7q33 alone. All the patients presented mild to moderate intellectual disability (ID), dysmorphic features, and a behavioral phenotype characterized by aggressiveness and disinhibition. One family presents a small duplication in cis affecting CALD1 and AGBL3 genes, while the other four patients carry two larger deletions encompassing EXOC4, CALD1, AGBL3, and CNOT4. This work helps to refine the phenotype and narrow the minimal critical region involved in 7q33 CNVs. Comparison with similar cases and functional studies should help us clarify the relevance of the deleted genes for ID and behavioral alterations.

A randomized controlled trial: branched-chain amino acid levels and glucose metabolism in patients with obesity and sleep apnea.

There is evidence that changes in branched-chain amino acid (BCAA) levels may correlate with the efficacy of therapeutic interventions for affecting improvement in metabolic control. The objective of this study was to evaluate whether serum concentrations of BCAAs (leucine, isoleucine, valine) could mediate in insulin sensitivity and glucose tolerance after continuous positive airway pressure (CPAP) treatment in patients with obstructive sleep apnea (OSA). A prospective randomized controlled trial of OSA patients with morbid obesity was conducted. Eighty patients were randomized into two groups: 38 received conservative treatment and 42 received CPAP treatment for 12 weeks. Plasma levels of BCAA, glucose tolerance and insulin resistance were evaluated at baseline and after treatment. After treatment, significant decreases of leucine levels were observed in both groups when compared with baseline levels (P < 0.005). With respect to patients with normal glucose tolerance (NGT), patients with impaired glucose tolerance (IGT) had higher baseline levels of isoleucine (78 ± 16 versus 70 ± 13 µmol L-1 , P = 0.014) and valine (286 ± 36 versus 268 ± 41 µmol L-1 , P = 0.049), respectively. Changes in levels of leucine and isoleucine after treatment were related negatively to changes in fasting plasma glucose and glycosylated haemoglobin values only in the conservative group (P < 0.05). In summary, we found that the treatment with CPAP for 12 weeks caused similar changes in circulating BCAAs concentrations to conservative treatment and a differential metabolic response of CPAP and conservative treatment was observed between the relationship of BCAAs and glucose homeostasis. Additional studies are needed to determine the interplay between branched-chain amino acids and glucose metabolism in patients with sleep apnea.

A Novel Domain-Specific Mutation in a Sclerosteosis Patient Suggests a Role of LRP4 as an Anchor for Sclerostin in Human Bone.

Mutations in the LRP4 gene, coding for a Wnt signaling coreceptor, have been found to cause several allelic conditions. Among these, two are characterized by a strong skeletal involvement, namely sclerosteosis and Cenani-Lenz syndrome. In this work, we evaluated the role of LRP4 in the pathophysiology of these diseases. First, we report a novel LRP4 mutation, leading to the substitution of arginine at position 1170 in glutamine, identified in a patient with sclerosteosis. This mutation is located in the central cavity of the third ß-propeller domain, which is in line with two other sclerosteosis mutations we previously described. Reporter assays demonstrate that this mutation leads to impaired sclerostin inhibition of Wnt signaling. Moreover, we compared the effect of this novel variant to mutations causing Cenani-Lenz syndrome and show that impaired membrane trafficking of the LRP4 protein is the likely mechanism underlying Cenani-Lenz syndrome. This is in contrast to sclerosteosis mutations, previously shown to impair the binding between LRP4 and sclerostin. In addition, to better understand the biology of LRP4, we investigated the circulating sclerostin levels in the serum of a patient suffering from sclerosteosis owing to a LRP4 mutation. We demonstrate that impaired sclerostin binding to the mutated LRP4 protein leads to dramatic increase in circulating sclerostin in this patient. With this study, we provide the first evidence suggesting that LRP4 is responsible for the retention of sclerostin in the bone environment in humans. These findings raise potential concerns about the utility of determining circulating sclerostin levels as a marker for other bone-related parameters. Although more studies are needed to fully understand the mechanism whereby LRP4 facilitates sclerostin action, it is clear that this protein represents a potent target for future osteoporosis therapies and an interesting alternative for the antisclerostin treatment currently under study.

Infantile Refsum Disease: Influence of Dietary Treatment on Plasma Phytanic Acid Levels.

Infantile Refsum disease (IRD) is one of the less severe of Zellweger spectrum disorders (ZSDs), a group of peroxisomal biogenesis disorders resulting from a generalized peroxisomal function impairment. Increased plasma levels of very long chain fatty acids (VLCFA) and phytanic acid are biomarkers used in IRD diagnosis. Furthermore, an increased plasma level of phytanic acid is known to be associated with neurologic damage. Treatment of IRD is symptomatic and multidisciplinary.The authors report a 3-year-old child, born from consanguineous parents, who presented with developmental delay, retinitis pigmentosa, sensorineural deafness and craniofacial dysmorphisms. While the relative level of plasma C26:0 was slightly increased, other VLCFA were normal. Thus, a detailed characterization of the phenotype was essential to point to a ZSD. Repeatedly increased levels of plasma VLCFA, along with phytanic acid and pristanic acid, deficient dihydroxyacetone phosphate acyltransferase activity in fibroblasts and identification of the homozygous pathogenic mutation c.2528G>A (p.Gly843Asp) in the PEX1 gene, confirmed this diagnosis. Nutritional advice and follow-up was proposed aiming phytanic acid dietary intake reduction. During dietary treatment, plasma levels of phytanic acid decreased to normal, and the patient's development evaluation showed slow progressive acquisition of new competences.This case report highlights the relevance of considering a ZSD in any child with developmental delay who manifests hearing and visual impairment and of performing a systematic biochemical investigation, when plasma VLCFA are mildly increased. During dietary intervention, a biochemical improvement was observed, and the long-term clinical effect of this approach needs to be evaluated.

The Koolen-de Vries syndrome: a phenotypic comparison of patients with a 17q21.31 microdeletion versus a KANSL1 sequence variant.

The Koolen-de Vries syndrome (KdVS; OMIM #610443), also known as the 17q21.31 microdeletion syndrome, is a clinically heterogeneous disorder characterised by (neonatal) hypotonia, developmental delay, moderate intellectual disability, and characteristic facial dysmorphism. Expressive language development is particularly impaired compared with receptive language or motor skills. Other frequently reported features include social and friendly behaviour, epilepsy, musculoskeletal anomalies, congenital heart defects, urogenital malformations, and ectodermal anomalies. The syndrome is caused by a truncating variant in the KAT8 regulatory NSL complex unit 1 (KANSL1) gene or by a 17q21.31 microdeletion encompassing KANSL1. Herein we describe a novel cohort of 45 individuals with KdVS of whom 33 have a 17q21.31 microdeletion and 12 a single-nucleotide variant (SNV) in KANSL1 (19 males, 26 females; age range 7 months to 50 years). We provide guidance about the potential pitfalls in the laboratory testing and emphasise the challenges of KANSL1 variant calling and DNA copy number analysis in the complex 17q21.31 region. Moreover, we present detailed phenotypic information, including neuropsychological features, that contribute to the broad phenotypic spectrum of the syndrome. Comparison of the phenotype of both the microdeletion and SNV patients does not show differences of clinical importance, stressing that haploinsufficiency of KANSL1 is sufficient to cause the full KdVS phenotype.

A Randomized Controlled Trial of Continuous Positive Airway Pressure on Glucose Tolerance in Obese Patients with Obstructive Sleep Apnea.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is associated with an increased prevalence of metabolic syndrome (MetS), even in patients with morbid obesity. Our goal was to address whether continuous positive airway pressure (CPAP) treatment improved glucose metabolism in this population. METHODS: A prospective randomized controlled trial was performed in severe OSA patients with morbid obesity without diabetes in two university referral hospitals. Patients received conservative (CT) versus CPAP treatment for 12 weeks. MetS components, homeostasis model assessment of insulin resistance (HOMA-IR) and oral glucose tolerance were assessed at baseline and after treatment. RESULTS: A total of 80 patients completed the study (42 CPAP and 38 CT patients). After 12 w of CPAP treatment, weight loss was similar in both groups and physical activity, prevalence of MetS, and HOMA-IR did not change in either group. In the CPAP group impaired glucose tolerance (IGT) reversed in nine patients and IGT developed in none, whereas IGT reversed in five patients and IGT developed in five patients in the CT group (P = 0.039 in the Fisher test). Changes in 2-h plasma glucose after glucose load were greater in the CPAP group than in the CT group (CPAP: -0.5 ± 1.5 versus CT: 0.33 ± 1.9, P = 0.007). CONCLUSIONS: The improvement of glucose tolerance in morbidly obese patients with severe obstructive sleep apnea, without changes in homeostasis model assessment of insulin resistance, supports an improvement in peripheral insulin resistance after continuous positive airway pressure treatment. CLINICAL TRIALS REGISTRATION: NCT 01029561.