Biallelic ASCC1 variants including a novel intronic variant result in expanded phenotypic spectrum of spinal muscular atrophy with congenital bone fractures 2 (SMABF2).

Spinal muscular atrophy with congenital bone fractures 2 (SMABF2), a type of arthrogryposis multiplex congenita (AMC), is characterized by congenital joint contractures, prenatal fractures of long bones, and respiratory distress and results from biallelic variants in ASCC1. Here, we describe an infant with severe, diffuse hypotonia, congenital contractures, and pulmonary hypoplasia characteristic of SMABF2, with the unique features of cleft palate, small spleen, transverse liver, and pulmonary thromboemboli with chondroid appearance. This infant also had impaired coagulation with diffuse petechiae and ecchymoses which has only been reported in one other infant with AMC. Using trio whole genome sequencing, our proband was identified to have biallelic variants in ASCC1. Using deep next generation sequencing of parental cDNA, we characterized alteration of splicing encoded by the novel, maternally inherited ASCC1 variant (c.297-8 T > G) which provides a mechanism for functional pathogenicity. The paternally inherited ASCC1 variant is a rare nonsense variant (c.466C > T; p.Arg156*) that has been previously identified in one other infant with AMC. This report extends the phenotypic characteristics of ASCC1-associated AMC (SMABF2) and describes a novel intronic variant that partially disrupts RNA splicing.

Biallelic mutations in nucleoporin NUP88 cause lethal fetal akinesia deformation sequence.

Nucleoporins build the nuclear pore complex (NPC), which, as sole gate for nuclear-cytoplasmic exchange, is of outmost importance for normal cell function. Defects in the process of nucleocytoplasmic transport or in its machinery have been frequently described in human diseases, such as cancer and neurodegenerative disorders, but only in a few cases of developmental disorders. Here we report biallelic mutations in the nucleoporin NUP88 as a novel cause of lethal fetal akinesia deformation sequence (FADS) in two families. FADS comprises a spectrum of clinically and genetically heterogeneous disorders with congenital malformations related to impaired fetal movement. We show that genetic disruption of nup88 in zebrafish results in pleiotropic developmental defects reminiscent of those seen in affected human fetuses, including locomotor defects as well as defects at neuromuscular junctions. Phenotypic alterations become visible at distinct developmental stages, both in affected human fetuses and in zebrafish, whereas early stages of development are apparently normal. The zebrafish phenotypes caused by nup88 deficiency are rescued by expressing wild-type Nup88 but not the disease-linked mutant forms of Nup88. Furthermore, using human and mouse cell lines as well as immunohistochemistry on fetal muscle tissue, we demonstrate that NUP88 depletion affects rapsyn, a key regulator of the muscle nicotinic acetylcholine receptor at the neuromuscular junction. Together, our studies provide the first characterization of NUP88 in vertebrate development, expand our understanding of the molecular events causing FADS, and suggest that variants in NUP88 should be investigated in cases of FADS.

Expanding the clinical and molecular spectrum of lethal congenital contracture syndrome 8 associated with biallelic variants of ADCY6.

Arthrogryposis multiplex congenita (AMC) is defined as congenital, non-progressive contractures in more than two joints and in multiple body areas, resulting from reduced fetal mobility. So far, more than 400 causative genes for AMC have been identified. Some isolated AMC phenotypes arise as a result of mutations in genes encoding components required for motor neuron structure, function, and myelination, as in the case of ADCY6 encoding the enzyme adenylyl cyclase type 6. ADCY6 inactivation, due to biallelic variants, have been previously associated with the lethal congenital contracture syndrome 8 (LCCS8). So far, only four LCCS8 patients, from two families, have been reported. Here, we describe a new patient affected by a severe form of AMC, harboring two novel compound heterozygous variants in ADCY6. Our findings expand the clinical and mutational spectrum of LCCS8, showing a possible correlation between the impact of the ADCY6 missense variants reported to date, predicted by molecular modeling, and the severity of the phenotype.

A Case of Severe Early-Onset Neuropathy Caused by a Compound Heterozygous Deletion of the PMP22 Gene: Clinical and Neurographic Aspects.

Heterozygous deletions of the gene PMP22 are associated to hereditary neuropathy with liability to pressure palsies (HNPP), a demyelinating neuromuscular disease causing variable transitory focal muscles weakness. Deletions involving both copies of PMP22 cause more severe phenotypes, with early-onset neuropathy and impairment in motor development. We report a patient with a severe early-onset demyelinating neuropathy, caused by two different inherited deletions of PMP22, whose parents had an HNPP. The patient showed neurological signs and delay in motor development but normal intellective abilities. A motor and sensitive conduction study showed severe signs of demyelination, suggestive for Dejerine Sottas Syndrome (DSS). The patient's father had a typical HNPP caused by a heterozygous 17p11.2 deletion, encompassing PMP22. The patient's mother reported no neuropathic symptoms, but in a nerve conduction studies, parents and several relatives showed signs of sensory-motor deficit with focal slowing of conduction at common sites of entrapment. Quantitative analysis of PMP22, performed in our patient by multiplex ligation-dependent probe amplification, revealed a compound heterozygous status with the same deletion of the father and a deletion of PMP22 exon 5, after proved to be inherited from the mother. Therefore, when we face an early-onset, severe form of neuropathy, we have to consider rare forms of hereditary neuropathy caused by homozygous or compound heterozygous mutations in PMP22, even if parents are asymptomatic; an exhaustive family history and an electrodiagnostic study are essential to guide genetic tests and to make a diagnosis.

Patient-reported Outcomes in Arthrogryposis.

BACKGROUND: Little is known about patient-reported health status in children and adolescents with arthrogryposis. Utilizing the Patient-Reported Outcome Measurement Information System (PROMIS) and Pediatric Outcomes Data Collection Instrument (PODCI) questionnaires, we investigated functional and psychosocial measures in arthrogryposis. METHODS: A total of 118 patients with arthrogryposis were identified from a prospective longitudinal cohort (the Congenital Upper Limb Difference Registry) from 2014 to 2018. Demographics and patient-reported outcome measures were evaluated, including the PROMIS [upper extremity (UE) function, pain, depression, anxiety, and peer relations] and PODCI questionnaires (UE function, pain, happiness, and global function). RESULTS: A total of 29 arthrogrypotic patients had complete PROMIS and PODCI data. This cohort was divided into distal arthrogryposis and amyoplasia groups, with 15 and 14 patients in each group, respectively. There were 8 males in the distal arthrogryposis group with a median age of 9 years and 7 males in the amyoplasia group with a median age of 8 years. For both cohorts, the median UE function PROMIS scores were significantly below population norms, 31 for distal arthrogryposis and 22 for amyoplasia. PODCI UE function was statistically lower for amyoplasia compared with the distal arthrogryposis cohort. PROMIS pain, depression, anxiety, and peer relations were in the normal range for both amyopasia and distal arthrogryposis. Median PODCI pain and happiness ranged from 85 to 88 for all patients with no statistical difference between groups. CONCLUSIONS: Arthrogryposis patients have lower UE function scores compared with population normals, but they have emotional states that are consistent with populations norms. Amyoplasia patients were functionally worse than distal arthrogryposis patients. LEVELS OF EVIDENCE: Level II.

The 5-Year Outcome of the Ponseti Method in Children With Idiopathic Clubfoot and Arthrogryposis.

BACKGROUND: The Ponseti method effectively treats idiopathic clubfoot, but its effectiveness in treating the stiffer clubfoot associated with arthrogryposis is less clear. The purpose of this study was to assess the comparative effectiveness of the Ponseti method in 5-year-old children with either idiopathic clubfoot or clubfoot due to arthrogryposis. METHODS: The outcomes of the Ponseti method were retrospectively evaluated in children with idiopathic clubfoot and clubfoot associated with arthrogryposis. The children with clubfoot were seen at our hospital between 2012 and 2019 and were 4.0 to 6.9 years old at the time of their evaluation. Outcomes of the 2 groups of children with clubfoot were assessed using passive range of motion, foot pressure analysis, the Gross Motor Function Measure Dimension-D, and parent report using the Pediatric Outcomes Data Collection Instrument. These results were also compared with the same measures from a group of typically developing children. Surgical and bracing history was also recorded. RESULTS: A total of 117 children were included (89 idiopathic clubfoot and 28 associated with arthrogryposis) with an average age of 4.8±0.8 years. The historical gait analyses of 72 typically developing children were used as a control, with an average age of 5.2±0.8 years. Significant residual equinovarus was seen in both children with idiopathic clubfoot and associated with arthrogryposis according to passive range of motion and foot pressure analysis when compared with normative data. Children with arthrogryposis demonstrated limited transfer and basic mobility, sports functioning, and global functioning while children with idiopathic clubfoot were significantly different from their typically developing peers in only transfer and basic mobility. CONCLUSIONS: Although children with idiopathic clubfoot continue with some level of residual deformity, the Ponseti method is effective in creating a pain-free, highly functional foot. In children with clubfoot associated with arthrogryposis, the Ponseti method is successful in creating a braceable foot that can delay the need for invasive surgical intervention. LEVEL OF EVIDENCE: Level III, Therapeutic Studies-Investigating the Results of Treatment.

Play with objects in children with arthrogryposis: Effects of intervention with the Playskin Lift™ exoskeletal garment.

Children with arthrogryposis multiplex congenita (AMC) often exhibit arm movement impairments that can negatively impact activities of daily living, such as reaching, object exploration, object play, and self-care. This study evaluated the effects of intervention involving the Playskin Lift™ (Playskin) exoskeletal garment on arm function during object play for children with AMC. Seventeen children with AMC (5 males; 6-35 months at the beginning of the study) were tested in their homes biweekly with and without the Playskin throughout a 1-month Baseline, 4-month Intervention, and 1-month Post-Intervention. Within sessions (assistive effects), children contacted and manipulated objects more while wearing the Playskin; they also showed greater intensity, complexity, and variability of behaviors performed during free play, as well as increased play space and reduced number of compensatory arm and trunk flings to facilitate reaching. Across time (rehabilitative effects), children significantly improved their visual-manual coupling as well as their ability to lift objects from a surface and to manipulate objects using one hand; in addition, children exhibited greater multimodality, variability, and intensity of their play behaviors. Current results suggest the Playskin Lift™ may serve as an effective assistive and rehabilitative device to improve play for children with arm movement impairments.

Rehabilitation across the lifespan for individuals with arthrogryposis.

Arthrogryposis multiplex congenita (AMC) can be a perplexing diagnosis that consists of limited range of motion (ROM) and decreased muscle strength in multiple joints. The person with AMC often possesses a certain tenacity and "spunk" that assists them with adjusting and adapting to the realities of daily life. The rehabilitation process assists the individual with AMC in achieving and maintaining the maximal active and passive range of motion and strength in order to participate in activities of daily living (ADL) throughout the developmental stages. The result of this life-long process is greatly impacted by collaboration among the multidisciplinary teams. Ultimately, rehabilitation should focus on three levels of treatment: (a) body structure, (b) activity, and (c) participation. This article describes rehabilitation across the lifespan-focusing on the therapeutic needs in the infant, toddler, school age and teenage/adult years-while also highlighting opportunities for improvement.

Muscle and joint function in children living with arthrogryposis multiplex congenita: A scoping review.

Arthrogryposis multiplex congenita (AMC) is characterized by congenital joint contractures present in two or more body areas. Lack of fetal movement is the underlying cause of AMC, which can lead to abnormal connective tissue surrounding the joint resulting in stiffness and muscle atrophy. Treatment aims at improving function and mobility through surgical and/or conservative interventions. A scoping review was conducted to explore the existing knowledge of the evaluation and treatment of muscle and joint function in children with AMC. Three search engines were included and identified 1,271 articles. Eighty-seven studies met the selection criteria and were included in this review. All included studies focused on joints, 30 of which also assessed the muscle. Assessment most often included the position of the contractures (n = 72), as well as range of motion (n = 66). Interventions to improve muscle and joint function were reported in 82 of the 87 papers and included surgery (n = 70) and conservative interventions (n = 74) with bony surgery (i.e., osteotomy) the most common surgery and rehabilitation the most common conservative intervention. Recurrences of contractures were mentioned in 46 of the 68 studies providing a follow-up. Future studies should use validated measures to assess muscle and joint function, and conservative interventions should be described in greater detail and to include a longer follow-up.

Treatment and outcomes of arthrogryposis in the upper extremity.

Upper extremity involvement in patients with arthrogryposis multiplex congentia is quite frequent. Treatment initially consists of stretching and splinting as significant gains can be seen in the first years of life. The goal of any surgical procedure is to improve upper extremity function and performance of daily living activities, yet it is important to treat each patient individually and understand that areas do not always need to be addressed surgically. Despite overall lower functioning scores in this patient population, quality of life scores are comparable to the general aged adjusted population. This article will discuss the clinical presentation, treatment procedures and outcomes when addressing the upper extremities of patients presenting with arthrogryposis.

Research platform for children with arthrogryposis multiplex congenita: Findings from the pilot registry.

A pediatric registry for arthrogryposis multiplex congenita (AMC) proposes to advance research by providing the platform to inform the distribution, etiology, and natural history of AMC. The registry was piloted on 40 families of children (mean = 8.25 years, 48% males) presenting with AMC across two hospitals in North America. Data on the child's demographic and newborn variables, mothers' and fathers' demographic variables, lifestyle habits, and medical history were collected using a telephone interview with the primary caregiver and review of medical charts. Mean gestational age was 38 weeks, 97% of children presented with lower extremity deformities, and 74% of neonatal interventions targeted the lower extremity. Newborns spent an average of 14 days in the hospital (range 2-56 days) mostly for diagnostic workup and feeding difficulties. Half (49%) of the sample had internal organ involvement. Genetic testing was done on 48% of the children, including chromosome studies, single gene, whole-exome/genome sequencing, and/or microarray studies. Genetic findings were inconclusive in most. Two-thirds of mothers (67%) reported inconsistently feeling fetal movements. This pilot study contributed to the refinement of participant selection, identification of data source, expansion of data sets, and areas for future exploration prior to the implementation of a multisite AMC pediatric registry.

Molecular analysis provides further evidence that Chitayat syndrome is caused by the recurrent p.(Tyr89Cys) pathogenic variant in the ERF gene.

Chitayat syndrome (CHYTS, MIM #617180) is a rare autosomal dominant clinical condition caused by a single missense pathogenic variant in the ERF gene (19q13.2, MIM*611888), which encodes the ETS2 Repressor Factor (ERF) protein. The characteristic features reported to date for this condition are facial dysmorphism, hyperphalangism and respiratory complications during the newborn period. Herein, we report the sixth patient worldwide with a confirmed molecular diagnosis of CHYTS. Our documentation of pectus carinatum, hypoplastic phalanges (as in two previously described patients), and lack of hyperphalangism broadens the phenotypic spectrum of CHYTS. Moreover, our identification of a heterozygous mutation [c.266A>G or p.(Tyr89Cys)] [rs886041001] in this patient provides further evidence that this condition is caused by a recurrent pathogenic variant in ERF.

Chitayat-Hall and Schaaf-Yang syndromes:a common aetiology: expanding the phenotype of MAGEL2-related disorders.

BACKGROUND: Chitayat-Hall syndrome, initially described in 1990, is a rare condition characterised by distal arthrogryposis, intellectual disability, dysmorphic features and hypopituitarism, in particular growth hormone deficiency. The genetic aetiology has not been identified. METHODS AND RESULTS: We identified three unrelated families with a total of six affected patients with the clinical manifestations of Chitayat-Hall syndrome. Through whole exome or whole genome sequencing, pathogenic variants in the MAGEL2 gene were identified in all affected patients. All disease-causing sequence variants detected are predicted to result in a truncated protein, including one complex variant that comprised a deletion and inversion. CONCLUSIONS: Chitayat-Hall syndrome is caused by pathogenic variants in MAGEL2 and shares a common aetiology with the recently described Schaaf-Yang syndrome. The phenotype of MAGEL2-related disorders is expanded to include growth hormone deficiency as an important and treatable complication.

Development of self-feeding behavior in children with typical development and those with arm movement impairments.

Self-feeding is a critical self-care skill that unites motor abilities (e.g., grasping and transporting utensils/food to the mouth) and cognitive abilities (e.g., using a spoon as a tool). This cross-sectional study assessed self-feeding behavior in a sample of 38 children with typical development (TD) and compared it between 18 of those children and 18 age- and sex-matched peers with arm movement impairments (MI). Children were assessed with a bowl of cereal and two spoons presented in four different orientations. Results suggested that children with MI were less successful than their TD peers in both motor aspects (e.g., grasp and transport of food and utensils) and cognitive aspects (correct grasp across spoon orientations) of self-feeding. Novel findings highlight: (a) interesting differences in visual attention between children with TD or MI; (b) the role of hand-preference in the correct grasping of the spoon(s) and effective self-feeding; (c) the positive relation between motor and cognitive aspects of self-feeding; and (d) that greater variability of self-feeding behavior relates to improved performance of cognitive aspects of the task. These results identify challenging components of self-feeding for children with MI that should be targeted by early interventions and assistive technologies aimed at increasing self-feeding independence.

The Effects of Age on the Outcomes of Elbow Release in Arthrogryposis.

PURPOSE: The goal of this study was to observe the effects of posterior elbow release on children with arthrogryposis at various age points: before the age of 2, between the ages of 2 and 3, and after the age of 3. METHODS: This study was a retrospective chart review of patients with arthrogryposis who underwent a posterior elbow release for an elbow extension contracture between 2007 and 2014 at one institution. Eighteen procedures in 13 patients, who had a minimum follow-up of at least 2 years, were included in the study. Patients were divided into 3 groups based on their age at the time of surgery: <2 years old, 2-3 years old, and >3 years old. Comparisons of the pre- and postoperative passive arcs of motion were made. RESULTS: The average preoperative arc of motion was 16° (0° to 30°) for the children younger than 2, 33.5° (5° to 60°) for the children 2-3, and 45° (25° to 80°) for the children older than 3. The average postoperative arc of motion was 88.2° (70° to 103°), 60° (15° to 85°), and 54.33° (23° to 70°) for the respective age groups. There was a clinically important difference in the postoperative arc of motion between the children less than 2 years old and both the children 2-3 years old and older than 3 years. CONCLUSIONS: This study demonstrates that children who underwent posterior elbow release before the age of 2 had a clinically important increase in their postoperative flexion and overall passive arc of elbow motion compared with older children at medium-term follow-up. The data suggest that earlier release may be better at restoring total passive arc of elbow motion. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Predicting Ambulatory Function Based on Infantile Lower Extremity Posture Types in Amyoplasia Arthrogryposis.

BACKGROUND: Arthrogryposis multiplex congenita (AMC) is a nonprogressive syndrome with multiple rigid joints, fibrotic periarticular tissue, and muscular fibrosis. The most common subgroup is amyoplasia. Ambulation is one of the most significant functions of the lower extremities as it translates to increased functionality and independence in adulthood. There is no predicative scale to determine ambulation at maturity for the infant with amyoplasia. It is believed lower extremity resting position of infants with amyoplasia potentially correlates with ambulation at maturity. The purpose of this study was to classify the infantile position of lower extremities and muscle strength to predict ambulation potential at maturity. METHODS: Children with amyoplasia were retrospectively reviewed and classified into groups based on infantile position of hip-knee alignment and limb muscle function. Sitting, standing, and walking skills from infancy into adulthood were evaluated. The ambulation function was correlated with the infantile position of the lower extremities. RESULTS: Amyoplasia cases were sorted into 5 types and correlated with ambulatory potential. Type I: mild ambulatory impairment with infantile position of flexed knees and hips but full range of motion. At maturity, all were community ambulators. Type II: moderate ambulatory impairment having infantile position of hip flexion, hip external rotation, and knee flexion contractures. Hip abductors and external rotators had antigravity strength. All stood and walked during the first decade of life with knee ankle foot orthoses. Type III: severe ambulatory impairment having infantile position of hip flexion, abduction, external rotation, and knee flexion contractures but lacked hip muscle recruitment. All used wheelchairs at maturity. Type IV: mild ambulatory impairment with infantile position of extended knees and flexed dislocated hips. At maturity, 90% were community ambulators. Type V: variable ambulatory impairment having asymmetric hip and knee alignment with unilateral hip dysplasia with extended knee and opposite limb flexed. Ambulation skill varied at maturity with 27% full-time wheelchair users. CONCLUSIONS: Amyoplasia can be sorted by infantile position of lower extremities and muscle strength into 5 types to predict ambulatory function. LEVEL OF EVIDENCE: Level III-Prognostic Study.

Autosomal-Dominant Multiple Pterygium Syndrome Is Caused by Mutations in MYH3.

Multiple pterygium syndrome (MPS) is a phenotypically and genetically heterogeneous group of rare Mendelian conditions characterized by multiple pterygia, scoliosis, and congenital contractures of the limbs. MPS typically segregates as an autosomal-recessive disorder, but rare instances of autosomal-dominant transmission have been reported. Whereas several mutations causing recessive MPS have been identified, the genetic basis of dominant MPS remains unknown. We identified four families affected by dominantly transmitted MPS characterized by pterygia, camptodactyly of the hands, vertebral fusions, and scoliosis. Exome sequencing identified predicted protein-altering mutations in embryonic myosin heavy chain (MYH3) in three families. MYH3 mutations underlie distal arthrogryposis types 1, 2A, and 2B, but all mutations reported to date occur in the head and neck domains. In contrast, two of the mutations found to cause MPS in this study occurred in the tail domain. The phenotypic overlap among persons with MPS, coupled with physical findings distinct from other conditions caused by mutations in MYH3, suggests that the developmental mechanism underlying MPS differs from that of other conditions and/or that certain functions of embryonic myosin might be perturbed by disruption of specific residues and/or domains. Moreover, the vertebral fusions in persons with MPS, coupled with evidence of MYH3 expression in bone, suggest that embryonic myosin plays a role in skeletal development.

Novel mutations in TPM2 and PIEZO2 are responsible for distal arthrogryposis (DA) 2B and mild DA in two Chinese families.

BACKGROUND: Distal arthrogryposis (DA) is a group of clinically and genetically heterogeneous disorders that involve multiple congenital limb contractures and comprise at least 10 clinical subtypes. Here, we describe our findings in two Chinese families: Family 1 with DA2B (MIM 601680) and Family 2 with mild DA. METHODS: To map the disease locus, two-point linkage analysis was performed with microsatellite markers closed to TPM2, TNNI2/TNNT3 and TNNC2. In Family 1, a positive LOD (logarithm of odds) score was only obtained at the microsatellite marker close to TPM2 and mutation screening was performed using direct sequencing of TPM2 in the proband. In Family 2, for the LOD score that did not favor linkage to any markers, whole-exome sequencing (WES) was performed on the proband. PCR-restriction fragment length polymorphism (RFLP) and bioinformatics analysis were then applied to identify the pathogenic mutations in two families. In order to correlate genotype with phenotype in DA, retrospective analyses of phenotypic features according to the TPM2 and PIEZO2 mutation spectrums were carried out. RESULTS: A heterozygous missense mutation c.308A > G (p.Q103R) in TPM2 in Family 1, and a novel variation c.8153G > A (p.R2718Q) in PIEZO2 in Family 2 were identified. Each of the two novel variants was co-segregated with the DA manifestations in the corresponding family. Bioinformatics analysis from several tools supported the pathogenicity of the mutations. Furthermore, our study suggests that there is no relation between the types or locations of TPM2 mutations and the clinical characteristics, and that different inheritance modes and mutation types concerning PIEZO2 cause distinct clinical manifestations. CONCLUSIONS: We report two novel mutations within TPM2 and PIEZO2 responsible for DA2B and mild DA in two Chinese families, respectively. Our study expands the spectrum of causal mutations in the TPM2 and PIEZO2 genes.

Recessive PIEZO2 stop mutation causes distal arthrogryposis with distal muscle weakness, scoliosis and proprioception defects.

The genetic work-up of arthrogryposis is challenging due to the diverse clinical and molecular etiologies. We report a-183/12-year-old boy, from a 2nd degree consanguineous family, who presented at 36/12 years with hypotonia, distal laxity, contractures, feeding difficulties at birth. He required surgery for progressive scoliosis at 16 years of age, and walked independently since then with an unstable gait and coordination defects. His latest examination at 18 years of age revealed a proprioceptive defect and loss-of-joint position sense in the upper limbs. Somatosensory evoked potentials supported bilateral involvement of dorsal column-medial lemniscal sensory pathways and nerve conduction studies revealed a mild axonal neuropathy. Muscle biopsy showed myopathic changes with neonatal myosin expression. Mendeliome sequencing led to the discovery of a recessive stop mutation in piezo-type mechanosensitive ion channel component 2 (PIEZO2, NM_022068, c.1384C>T, p.R462*). PIEZO2 is a nonselective cation channel, expressed in sensory endings of proprioceptors innervating muscle spindles and Golgi tendon organs. Dominant PIEZO2 mutations were described in patients with distal arthrogryposis type 5 and Marden-Walker syndrome. Sensory ataxia and proprioception defect with dorsal column involvement together with arthrogryposis, myopathy, scoliosis and progressive respiratory failure may represent a distinct clinical phenotype, and indicate recessive mutations in PIEZO2.

Expansion of the GLE1-associated arthrogryposis multiplex congenita clinical spectrum.

Mutations in GLE1 cause two recessive subtypes of arthrogryposis multiplex congenita (AMC), a condition characterized by joint contractures at birth, and all previously reported patients died in the perinatal period. GLE1 related AMC has been almost exclusively reported in the Finnish population and is caused by a relatively common pathogenic splicing mutation in that population. Here, we report two non-Finnish brothers with novel compound heterozygous splicing mutations in GLE1, one of whom has survived to 12 years of age. We also demonstrate low levels of residual wild type transcript in fibroblasts from the surviving brother, suggesting that this residual wild-type transcript may contribute to the relatively longer-term survival in this family. We provide a detailed clinical report on the surviving patient, providing the first insight into the natural history of this rare neuromuscular disease. We also suggest that lethal congenital contracture syndrome 1 (LCCS1) and lethal arthrogryposis with anterior horn disease (LAAHD), the two AMC subtypes related to GLE1, do not have sufficient clinical or molecular differentiation to be considered allelic disorders. Rather, GLE1 mutations cause a variable spectrum of AMC severity including a non-lethal variant described herein.