SUFU haploinsufficiency causes a recognisable neurodevelopmental phenotype at the mild end of the Joubert syndrome spectrum.

BACKGROUND: Joubert syndrome (JS) is a recessively inherited ciliopathy characterised by congenital ocular motor apraxia (COMA), developmental delay (DD), intellectual disability, ataxia, multiorgan involvement, and a unique cerebellar and brainstem malformation. Over 40 JS-associated genes are known with a diagnostic yield of 60%-75%.In 2018, we reported homozygous hypomorphic missense variants of the SUFU gene in two families with mild JS. Recently, heterozygous truncating SUFU variants were identified in families with dominantly inherited COMA, occasionally associated with mild DD and subtle cerebellar anomalies. METHODS: We reanalysed next generation sequencing (NGS) data in two cohorts comprising 1097 probands referred for genetic testing of JS genes. RESULTS: Heterozygous truncating and splice-site SUFU variants were detected in 22 patients from 17 families (1.5%) with strong male prevalence (86%), and in 8 asymptomatic parents. Patients presented with COMA, hypotonia, ataxia and mild DD, and only a third manifested intellectual disability of variable severity. Brain MRI showed consistent findings characterised by vermis hypoplasia, superior cerebellar dysplasia and subtle-to-mild abnormalities of the superior cerebellar peduncles. The same pattern was observed in two out of three tested asymptomatic parents. CONCLUSION: Heterozygous truncating or splice-site SUFU variants cause a novel neurodevelopmental syndrome encompassing COMA and mild JS, which likely represent overlapping entities. Variants can arise de novo or be inherited from a healthy parent, representing the first cause of JS with dominant inheritance and reduced penetrance. Awareness of this condition will increase the diagnostic yield of JS genetic testing, and allow appropriate counselling about prognosis, medical monitoring and recurrence risk.

Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848.

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000-3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons-Leu844, Cys845, Ala846, Leu847, and Gly848-located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p < 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844-848 exists and will be valuable in the management and genetic counseling of a significant number of individuals.

Expanding the phenotype of Wiedemann-Steiner syndrome: Craniovertebral junction anomalies.

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant condition caused by heterozygous loss of function variants in the KMT2A (MLL) gene, encoding a lysine N-methyltransferase that mediates a histone methylation pattern specific for epigenetic transcriptional activation. WDSTS is characterized by a distinctive facial phenotype, hypertrichosis, short stature, developmental delay, intellectual disability, congenital malformations, and skeletal anomalies. Recently, a few patients have been reported having abnormal skeletal development of the cervical spine. Here we describe 11 such individuals, all with KMT2A de novo loss-of-function variants: 10 showed craniovertebral junction anomalies, while an 11th patient had a cervical abnormality in C7. By evaluating clinical and diagnostic imaging data we characterized these anomalies, which consist primarily of fused cervical vertebrae, C1 and C2 abnormalities, small foramen magnum and Chiari malformation type I. Craniovertebral anomalies in WDSTS patients have been largely disregarded so far, but the increasing number of reports suggests that they may be an intrinsic feature of this syndrome. Specific investigation strategies should be considered for early identification and prevention of craniovertebral junction complications in WDSTS patients.

Genotype-phenotype correlation at codon 1740 of SETD2.

The SET domain containing 2, histone lysine methyltransferase encoded by SETD2 is a dual-function methyltransferase for histones and microtubules and plays an important role for transcriptional regulation, genomic stability, and cytoskeletal functions. Specifically, SETD2 is associated with trimethylation of histone H3 at lysine 36 (H3K36me3) and methylation of α-tubulin at lysine 40. Heterozygous loss of function and missense variants have previously been described with Luscan-Lumish syndrome (LLS), which is characterized by overgrowth, neurodevelopmental features, and absence of overt congenital anomalies. We have identified 15 individuals with de novo variants in codon 1740 of SETD2 whose features differ from those with LLS. Group 1 consists of 12 individuals with heterozygous variant c.5218C>T p.(Arg1740Trp) and Group 2 consists of 3 individuals with heterozygous variant c.5219G>A p.(Arg1740Gln). The phenotype of Group 1 includes microcephaly, profound intellectual disability, congenital anomalies affecting several organ systems, and similar facial features. Individuals in Group 2 had moderate to severe intellectual disability, low normal head circumference, and absence of additional major congenital anomalies. While LLS is likely due to loss of function of SETD2, the clinical features seen in individuals with variants affecting codon 1740 are more severe suggesting an alternative mechanism, such as gain of function, effects on epigenetic regulation, or posttranslational modification of the cytoskeleton. Our report is a prime example of different mutations in the same gene causing diverging phenotypes and the features observed in Group 1 suggest a new clinically recognizable syndrome uniquely associated with the heterozygous variant c.5218C>T p.(Arg1740Trp) in SETD2.

Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

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Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

PURPOSE: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors. METHODS: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study. RESULTS: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del. CONCLUSION: We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.

A patient with germ-line gain-of-function PDGFRB p.N666H mutation and marked clinical response to imatinib.

PurposeHeterozygous germ-line activating mutations in PDGFRB cause Kosaki and Penttinen syndromes and myofibromatosis. We describe a 10-year-old child with a germ-line PDGFRB p.N666H mutation who responded to the tyrosine kinase inhibitor imatinib by inhibition of PDGFRB.MethodsThe impact of p.N666H on PDGFRB function and sensitivity to imatinib was studied in cell culture.ResultsCells expressing the p.N666H mutation showed constitutive PDGFRB tyrosine phosphorylation. PDGF-independent proliferation was abolished by imatinib at 1 µM concentration. Patient fibroblasts showed constitutive receptor tyrosine phosphorylation that was also abrogated by imatinib with reduced proliferation of treated cells.This led to patient treatment with imatinib at 400 mg daily (340 mg/m2) for a year with objective improvement of debilitating hand and foot contractures, reduced facial coarseness, and significant improvement in quality of life. New small subcutaneous nodules developed, but remained stable. Transient leukopenia, neutropenia, and fatigue resolved without intervention; however, mildly decreased growth velocity resulted in reducing imatinib dose to 200 mg daily (170 mg/m2). The patient continues treatment with ongoing clinical response.ConclusionTo our knowledge, this is one of the first personalized treatments of a congenital disorder caused by a germ-line PDGF receptor mutation with a PDGFRB inhibitor.

Intrafamilial variability in the clinical manifestations of mucopolysaccharidosis type II: Data from the Hunter Outcome Survey (HOS).

Several cases of phenotypic variability among family members with mucopolysaccharidosis type II (MPS II) have been reported, but the data are limited. Data from patients enrolled in the Hunter Outcome Survey (HOS) were used to investigate intrafamilial variability in male siblings with MPS II. As of July 2015, data were available for 78 patients aged ≥5 years at last visit who had at least one affected sibling (39 sibling pairs). These patients were followed prospectively (i.e., they were alive at enrollment in HOS). The median age at the onset of signs and symptoms was the same for the elder and younger brothers (2.0 years); however, the younger brothers were typically diagnosed at a younger age than the elder brothers (median age, 2.5 and 5.1 years, respectively). Of the 39 pairs, eight pairs were classified as being discordant (the status of four or more signs and symptoms differed between the siblings); 21 pairs had one, two, or three signs and symptoms that differed between the siblings, and 10 pairs had none. Regression status of the majority of the developmental milestones studied was generally concordant among siblings. Functional classification, a measure of central nervous system involvement, was the same in 24/28 pairs, although four pairs were considered discordant as functional classification differed between the siblings. Overall, this analysis revealed similarity in the clinical manifestations of MPS II among siblings. This information should help to improve our understanding of the clinical presentation of the disease, including phenotype prediction in affected family members.

Refining the phenotype associated with GNB1 mutations: Clinical data on 18 newly identified patients and review of the literature.

De novo germline mutations in GNB1 have been associated with a neurodevelopmental phenotype. To date, 28 patients with variants classified as pathogenic have been reported. We add 18 patients with de novo mutations to this cohort, including a patient with mosaicism for a GNB1 mutation who presented with a milder phenotype. Consistent with previous reports, developmental delay in these patients was moderate to severe, and more than half of the patients were non-ambulatory and nonverbal. The most observed substitution affects the p.Ile80 residue encoded in exon 6, with 28% of patients carrying a variant at this residue. Dystonia and growth delay were observed more frequently in patients carrying variants in this residue, suggesting a potential genotype-phenotype correlation. In the new cohort of 18 patients, 50% of males had genitourinary anomalies and 61% of patients had gastrointestinal anomalies, suggesting a possible association of these findings with variants in GNB1. In addition, cutaneous mastocytosis, reported once before in a patient with a GNB1 variant, was observed in three additional patients, providing further evidence for an association to GNB1. We will review clinical and molecular data of these new cases and all previously reported cases to further define the phenotype and establish possible genotype-phenotype correlations.

Retinal dystrophy in two boys with Costello syndrome due to the HRAS p.Gly13Cys mutation.

Features of Costello Syndrome, a systemic disorder caused by germline mutations in the proto-oncogene HRAS from the RAS/MAPK pathway, include failure-to-thrive, short stature, coarse facial features, cardiac defects including hypertrophic cardiomyopathy, intellectual disability, and predisposition to neoplasia. Two unrelated boys with Costello syndrome and an HRAS mutation (p.Gly13Cys) are presented with their ophthalmologic findings. Both had early symptoms of nystagmus, photophobia, and vision abnormalities. Fundus examination findings of retinal dystrophy were present at age 3 years. Both boys have abnormal electroretinograms with reduced or undetectable rod responses along with reduced cone responses consistent with rod-cone dystrophy. Our observations suggest that early ophthalmic examination and re-evaluations are indicated in children with Costello syndrome.

MKS1 regulates ciliary INPP5E levels in Joubert syndrome.

BACKGROUND: Joubert syndrome (JS) is a recessive ciliopathy characterised by a distinctive brain malformation 'the molar tooth sign'. Mutations in >27 genes cause JS, and mutations in 12 of these genes also cause Meckel-Gruber syndrome (MKS). The goals of this work are to describe the clinical features of MKS1-related JS and determine whether disease causing MKS1 mutations affect cellular phenotypes such as cilium number, length and protein content as potential mechanisms underlying JS. METHODS: We measured cilium number, length and protein content (ARL13B and INPP5E) by immunofluorescence in fibroblasts from individuals with MKS1-related JS and in a three-dimensional (3D) spheroid rescue assay to test the effects of disease-related MKS1 mutations. RESULTS: We report MKS1 mutations (eight of them previously unreported) in nine individuals with JS. A minority of the individuals with MKS1-related JS have MKS features. In contrast to the truncating mutations associated with MKS, all of the individuals with MKS1-related JS carry ≥ 1 non-truncating mutation. Fibroblasts from individuals with MKS1-related JS make normal or fewer cilia than control fibroblasts, their cilia are more variable in length than controls, and show decreased ciliary ARL13B and INPP5E. Additionally, MKS1 mutant alleles have similar effects in 3D spheroids. CONCLUSIONS: MKS1 functions in the transition zone at the base of the cilium to regulate ciliary INPP5E content, through an ARL13B-dependent mechanism. Mutations in INPP5E also cause JS, so our findings in patient fibroblasts support the notion that loss of INPP5E function, due to either mutation or mislocalisation, is a key mechanism underlying JS, downstream of MKS1 and ARL13B.

Rapid molecular diagnostics of severe primary immunodeficiency determined by using targeted next-generation sequencing.

BACKGROUND: Primary immunodeficiency diseases (PIDDs) are inherited disorders of the immune system. The most severe form, severe combined immunodeficiency (SCID), presents with profound deficiencies of T cells, B cells, or both at birth. If not treated promptly, affected patients usually do not live beyond infancy because of infections. Genetic heterogeneity of SCID frequently delays the diagnosis; a specific diagnosis is crucial for life-saving treatment and optimal management. OBJECTIVE: We developed a next-generation sequencing (NGS)-based multigene-targeted panel for SCID and other severe PIDDs requiring rapid therapeutic actions in a clinical laboratory setting. METHODS: The target gene capture/NGS assay provides an average read depth of approximately 1000×. The deep coverage facilitates simultaneous detection of single nucleotide variants and exonic copy number variants in one comprehensive assessment. Exons with insufficient coverage (<20× read depth) or high sequence homology (pseudogenes) are complemented by amplicon-based sequencing with specific primers to ensure 100% coverage of all targeted regions. RESULTS: Analysis of 20 patient samples with low T-cell receptor excision circle numbers on newborn screening or a positive family history or clinical suspicion of SCID or other severe PIDD identified deleterious mutations in 14 of them. Identified pathogenic variants included both single nucleotide variants and exonic copy number variants, such as hemizygous nonsense, frameshift, and missense changes in IL2RG; compound heterozygous changes in ATM, RAG1, and CIITA; homozygous changes in DCLRE1C and IL7R; and a heterozygous nonsense mutation in CHD7. CONCLUSION: High-throughput deep sequencing analysis with complete clinical validation greatly increases the diagnostic yield of severe primary immunodeficiency. Establishing a molecular diagnosis enables early immune reconstitution through prompt therapeutic intervention and guides management for improved long-term quality of life.

WNT1 mutations in families affected by moderately severe and progressive recessive osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a heritable disorder that ranges in severity from death in the perinatal period to an increased lifetime risk of fracture. Mutations in COL1A1 and COL1A2, which encode the chains of type I procollagen, result in dominant forms of OI, and mutations in several other genes result in recessive forms of OI. Here, we describe four recessive-OI-affected families in which we identified causative mutations in wingless-type MMTV integration site family 1 (WNT1). In family 1, we identified a homozygous missense mutation by exome sequencing. In family 2, we identified a homozygous nonsense mutation predicted to produce truncated WNT1. In family 3, we found a nonsense mutation and a single-nucleotide duplication on different alleles, and in family 4, we found a homozygous 14 bp deletion. The mutations in families 3 and 4 are predicted to result in nonsense-mediated mRNA decay and the absence of WNT1. WNT1 is a secreted signaling protein that binds the frizzled receptor (FZD) and the coreceptor low-density lipoprotein-receptor-related protein 5 (LRP5). Biallelic loss-of-function mutations in LRP5 result in recessive osteoporosis-pseudoglioma syndrome with low bone mass, whereas heterozygous gain-of-function mutations result in van Buchem disease with elevated bone density. Biallelic loss-of-function mutations in WNT1 result in a recessive clinical picture that includes bone fragility with a moderately severe and progressive presentation that is not easily distinguished from dominant OI type III.

The natural history of growth in patients with Hunter syndrome: Data from the Hunter Outcome Survey (HOS).

Hunter syndrome (mucopolysaccharidosis type II) affects growth but the overall impact is poorly understood. This study investigated the natural history of growth and related parameters and their relationship with disease severity (as indicated by cognitive impairment). Natural history data from males followed prospectively in the Hunter Outcome Survey registry and not receiving growth hormone or enzyme replacement therapy, or before treatment start, were analysed (N=676; January 2014). Analysis of first-reported measurements showed short stature by 8years of age; median age-corrected standardized height score (z-score) in patients aged 8-12years was -3.1 (1st, 3rd quartile: -4.3, -1.7; n=68). Analysis of growth velocity using consecutive values found no pubertal growth spurt. Patients had large head circumference at all ages, and above average body weight and body mass index (BMI) during early childhood (median z-score in patients aged 2-4years, weight [n=271]: 1.7 [0.9, 2.4]; BMI [n=249]: 2.0 [1.1, 2.7]). Analysis of repeated measurements over time found greater BMI in those with cognitive impairment than those without, but no difference in height, weight or head circumference. Logistic regression modelling (data from all time points) found that increased BMI was associated with the presence of cognitive impairment (odds ratio [95% CI], 3.329 [2.313-4.791]), as were increased weight (2.365 [1.630-3.433]) and head circumference (1.749 [1.195-2.562]), but not reduced height. Unlike some other MPS disorders, there is no evidence at present for predicting disease severity in patients with Hunter syndrome based on changes in growth characteristics.

Identifying the need for a multidisciplinary approach for early recognition of mucopolysaccharidosis VI (MPS VI).

Mucopolysaccharidosis VI (MPS VI, Maroteaux-Lamy syndrome) is caused by deficient activity of the enzyme, N-acetylgalactosamine-4-sulfatase, resulting in impaired degradation of the glycosaminoglycan dermatan sulfate. Patients experience a range of manifestations including joint contractures, short stature, dysostosis multiplex, coarse facial features, decreased pulmonary function, cardiac abnormalities, corneal clouding and shortened life span. Recently, clinicians from institutions in the Asia-Pacific region met to discuss the occurrence and implications of delayed diagnosis and misdiagnosis of MPS VI in the patients they have managed. Eighteen patients (44% female) were diagnosed. The most common sign presented by the patients was bone deformities in 11 patients (65%). Delays to diagnosis occurred due to the lack of or distance to diagnostic facilities for four patients (31%), alternative diagnoses for two patients (15%), and misleading symptoms experienced by two patients (15%). Several patients experienced manifestations that were subtler than would be expected and were subsequently overlooked. Several cases highlighted the unique challenges associated with diagnosing MPS VI from the perspective of different specialties and provide insights into how these patients initially present, which may help to elucidate strategies to improve the diagnosis of MPS VI.

Long-term experience with enzyme replacement therapy (ERT) in MPS II patients with a severe phenotype: an international case series.

INTRODUCTION: No published clinical trial data are available to inform the use of enzyme replacement therapy (ERT) in patients with the severe (neuropathic) phenotype of mucopolysaccharidosis II (MPS II). Current guidelines recommend ERT administered intravenously be used on a trial basis in this population. AIMS/METHODS: A retrospective chart review was conducted at five international centers for this case series of 22 patients with neuropathic MPS II who received intravenous idursulfase 0.5 mg/kg weekly for at least 2 consecutive years. We collected data about urinary glycosaminoglycan levels, adverse events, and the following somatic signs/symptoms: skeletal disease, joint range of motion, liver/spleen size, respiratory infections, cardiac disease, diarrhea, skin/hair texture, and hospitalizations. RESULTS: The age at diagnosis was 2 months to 5 years, and the age at idursulfase initiation was between 18 months and 21 years. One of 22 patients experienced improvements in seven somatic signs/symptoms; 17/22 experienced improvements in five to six somatic signs/symptoms; and 4/22 experienced improvements in four somatic signs/symptoms. None experienced fewer than four improvements. No new safety concerns arose. Infusion-related reactions were experienced by 4/22 patients but were successfully managed using accepted strategies. CONCLUSIONS: Long-term treatment with idursulfase was associated with improvements in somatic manifestations in this case series of patients with neuropathic MPS II. The family and medical team should maintain open lines of communication to make treatment decisions that take into consideration the benefits and limitations of ERT in this population.

Mucopolysaccharidosis IVA (Morquio A syndrome) and VI (Maroteaux-Lamy syndrome): under-recognized and challenging to diagnose.

OBJECTIVE: Mucopolysaccharidosis IVA (MPS IVA, or Morquio A syndrome) and VI (MPS VI, or Maroteaux-Lamy syndrome) are autosomal recessive lysosomal storage disorders. Skeletal abnormalities are common initial presenting symptoms and, when recognized early, may facilitate timely diagnosis and intervention, leading to improved patient outcomes. Patients with slowly progressing disease and nonclassic phenotypes can be particularly challenging to diagnose. The objective was to describe the radiographic features of patients with a delayed diagnosis of MPS IVA or VI. MATERIALS AND METHODS: This was a retrospective study. The records of 5 MPS IVA and 3 MPS VI patients with delayed diagnosis were reviewed. Radiographs were evaluated by a radiologist with special expertise in skeletal dysplasias. RESULTS: An important common theme in these cases was the appearance of multiple epiphyseal dysplasia (MED) with epiphyseal changes seemingly confined to the capital (proximal) femoral epiphyses. Very few patients had the skeletal features of classical dysostosis multiplex. CONCLUSIONS: Radiologists should appreciate the wide phenotypic variability of MPS IVA and VI. The cases presented here illustrate the importance of considering MPS in the differential diagnosis of certain skeletal dysplasias/disorders, including MED, some forms of spondylo-epiphyseal dysplasia (SED), and bilateral Perthes-like disease. It is important to combine radiographic findings with clinical information to facilitate early testing and accurate diagnosis.

Clinical genetics evaluation in identifying the etiology of autism spectrum disorders: 2013 guideline revisions.

The autism spectrum disorders are a collective of conditions that have in common impaired socialization and communication in association with stereotypic behaviors. The reported incidence of autism spectrum disorders has increased dramatically over the past two decades. In addition, increased attention has been paid to these conditions by both lay and professional groups. These trends have resulted in an increase in the number of referrals to clinical geneticist for the evaluation of persons with autism spectrum disorders. The primary roles of the geneticist in this process are to define etiology when possible, to provide genetic counseling, and to contribute to case management. In deciding on the appropriate evaluation for a particular patient, the geneticist will consider a host of factors: (i) ensuring an accurate diagnosis of autism before proceeding with any investigation; (ii) discussing testing options, diagnostic yields, and family investment before proceeding with an evaluation; (iii) communicating and coordinating with the patient-centered medical home (PCMH); (iv) assessing the continuously expanding and evolving list of available laboratory-testing modalities in light of the published literature; (v) recognizing the expanded phenotypes of well-described syndromic and metabolic conditions that overlap with autism spectrum disorders; and (vi) defining an individualized evaluation plan based on the unique history and clinical features of a given patient. The guidelines in this paper have been developed to assist the clinician in the consideration of these factors. It updates the original publication from 2008.Genet Med 2013:15(5):399-407.

The effect of idursulfase on growth in patients with Hunter syndrome: data from the Hunter Outcome Survey (HOS).

Hunter syndrome (mucopolysaccharidosis type II) is a rare and life-limiting multisystemic disorder with an X-linked recessive pattern of inheritance. Short stature is a prominent feature of this condition. This analysis aimed to investigate the effects of enzyme replacement therapy with idursulfase on growth in patients enrolled in HOS - the Hunter Outcome Survey which is a multinational observational database. As of Jan 2012, height data before treatment were available for 567 of 740 males followed prospectively after HOS entry. Cross-sectional analysis showed that short stature became apparent after approximately 8 years of age; before this, height remained within the normal range. Age-corrected standardized height scores (z-scores) before and after treatment were assessed using piecewise regression model analysis in 133 patients (8-15 years of age at treatment start; data available on ≥ 1 occasion within +/-24 months of treatment start; growth hormone-treated patients excluded). Results showed that the slope after treatment (slope=-0.005) was significantly improved compared with before treatment (slope=-0.043) (difference=0.038, p=0.004). Analysis of covariates (age at treatment start, cognitive involvement, presence of puberty at the start of ERT, mutation type, functional classification), showed a significant influence on growth of mutation type (height deficit in terms of z-scores most pronounced in patients with deletions/large rearrangements/nonsense mutations, p<0.0001) and age (most pronounced in the 12-15-year group, p<0.0001). Cognitive involvement, pubertal status at the start of ERT and functional classification were not related to the growth deficit or response to treatment. In conclusion, the data showed an improvement in growth rate in patients with Hunter syndrome following idursulfase treatment.

The new era of Pompe disease: advances in the detection, understanding of the phenotypic spectrum, pathophysiology, and management.

Pompe disease is an autosomal recessive neuromuscular disorder marked by progressive muscle weakness due to lysosomal buildup of glycogen. Presentation is described as a spectrum, varying by age of onset, organ involvement, and degree of myopathy. Given the phenotypic variability, Pompe disease is broadly classified into an infantile form and a late onset (juvenile, childhood, adult onset) form. Prior to the advent of enzyme replacement therapy (ERT) with alglucosidase alfa and approval for human use in 2006, the natural history was limited due to death before age 2 years for infantile onset cases and significant morbidity and early mortality for late onset Pompe disease (LOPD). ERT with alglucosidase alfa redefined the once fatal outcome in infantile Pompe, establishing an emergent phenotype. Treatment in late onset patients resulted in improved outcomes, enhancing understanding of the phenotype, presentation, and extent of organ involvement. This Issue of the Seminars seeks to enumerate the recent advancements in the field of Pompe disease, including newborn screening, novel therapeutic targets, new insights in the pathophysiology including role of autophagy, and impacts of long-term disease burden and CNS glycogen accumulation on cognition in infantile survivors. It also addresses immunological challenges and the critical role of immunomodulation in ERT treatment outcome. Other topics discussed include the role of biomarkers in monitoring disease progression and treatment responses, the role of genotype in defining phenotype and treatment response, better insights into the clinical presentations in LOPD and finally the importance of a multidisciplinary approach to care with the role of physical therapy as an example. Many gaps in our scientific understanding of this disease still remain; however, we hope the next decade will bring new knowledge and therapies to the horizon.