Arthrogryposis: a review and update

Bi-allelic variants in MYH3 cause recessively-inherited arthrogryposis

Arthrogryposis is a clinical feature defined by congenital joint contractures in two or more different body areas which occurs in between 1/3000 and 1/5000 live births. Variants in multiple genes have been associated with distal arthrogryposis syndromes. Heterozygous variants in MYH3 have been identified to cause the dominantly-inherited distal arthrogryposis conditions, Freeman-Sheldon syndrome, Sheldon-Hall syndrome, and multiple pterygium syndrome. In contrast, MYH3 variants underlie both dominantly and recessively inherited Contractures, Pterygia, and Spondylocarpotarsal Fusion syndromes (CPSFS) which are characterized by extensive bony abnormalities in addition to congenital contractures. Here we report two affected sibs with distal arthrogryposis born to unaffected, distantly related parents. Sequencing revealed that both sibs were homozygous for two ultra-rare MYH3 variants, c.3445G>A (p.Glu1149Lys) and c.4760T>C (p.Leu1587Pro). Sequencing and deletion/duplication analysis of 169 other arthrogryposis genes yielded no other compelling candidate variants. This is the first report of biallelic variants in MYH3 being implicated in a distal arthrogryposis phenotype without the additional features of CPSFS. Thus, akin to CPSFS, both dominant and recessively inherited distal arthrogryposis can be caused by variants in MYH3.

Midterm clinical and radiological outcomes of arthrogryposis-associated clubfoot treated with the Ponseti method: a retrospective observational study and comprehensive literature review

BACKGROUND

The treatment results of the Ponseti method for arthrogrypotic clubfoot have been described in only a few case series. Further evaluations are necessary.

METHODS

Children from two German paediatric orthopaedic hospitals with arthrogryposis-associated clubfoot treated with the Ponseti method between 2004 and 2011 and who were at least five years of age at their last follow-up were retrospectively evaluated. The endpoints were the clinical foot position, necessary surgeries during the follow-up period and radiological constellations. A comprehensive literature review was conducted after a systematic literature search.

RESULTS

Seventeen patients (47% with amyoplasia [AP] and 53% with distal arthrogryposis [DA]) met the inclusion criteria. Thirty-one feet were evaluated. The period between the treatment start and the last follow-up examination covered 8.9 ± 2.5 years. After the last cast removal within the initial Ponseti cast series, 74% of the clinical results were good to excellent. However, the clinical outcomes in the patients with AP were significantly worse. Overall, in 23 feet (74%), at least one major surgery at the age of 2.9 ± 2.2 years was necessary during the clinical course. Major surgeries were much more frequent on the feet of the patients with AP than with DA. Lateral X-rays showed normal age-appropriate radiological angles in 4% of the feet, hindfoot equinus in 19%, under-corrected hindfoot in 44%, under-corrected clubfoot in 26% and rocker bottom deformity in 7%. The radiological residual deformities in AP were much more severe than in DA (p = 0.042). Most of the studies reviewed (11 case series, 144 patients) reported high initial clinical correction rates, followed by high recurrence rates and the need for further surgeries.

CONCLUSION

About a quarter of the arthrogrypotic patients benefited from the Ponseti therapy without further major surgery. However, the clinically observed high initial correction rate after Ponseti therapy of arthrogrypotic clubfoot was not accompanied by a correction of the bony foot position in the X-rays. The feet of the patients with DA had better outcomes than those of the patients with AP. Therefore, in outcome studies, a clear distinction between patients with AP and those with DA is necessary.

Immobilization secondary to cell death of muscle precursors with a dual transcriptional signature contributes to the emu wing skeletal pattern

Limb reduction has occurred multiple times in tetrapod history. Among ratites, wing reductions range from mild vestigialization to complete loss, with emus (Dromaius novaehollandiae) serving as a model for studying the genetic mechanisms behind limb reduction. Here, we explore the developmental mechanisms underlying wing reduction in emu. Our analyses reveal that immobilization resulting from the absence of distal muscles contributes to skeletal shortening, fusion and left-right intraindividual variation. Expression analysis and single cell-RNA sequencing identify muscle progenitors displaying a dual lateral plate mesodermal and myogenic signature. These cells aggregate at the proximal region of wing buds and undergo cell death. We propose that this cell death, linked to the lack of distal muscle masses, underlines the morphological features and variability in skeletal elements due to reduced mechanical loading. Our results demonstrate that differential mobility during embryonic development may drive morphological diversification in vestigial structures.

Myotube Guidance: Shaping up the Musculoskeletal System

Myofibers are highly specialized contractile cells of skeletal muscles, and dysregulation of myofiber morphogenesis is emerging as a contributing cause of myopathies and structural birth defects. Myotubes are the myofiber precursors and undergo a dramatic morphological transition into long bipolar myofibers that are attached to tendons on two ends. Similar to axon growth cones, myotube leading edges navigate toward target cells and form cell-cell connections. The process of myotube guidance connects myotubes with the correct tendons, orients myofiber morphology with the overall body plan, and generates a functional musculoskeletal system. Navigational signaling, addition of mass and volume, and identification of target cells are common events in myotube guidance and axon guidance, but surprisingly, the mechanisms regulating these events are not completely overlapping in myotubes and axons. This review summarizes the strategies that have evolved to direct myotube leading edges to predetermined tendon cells and highlights key differences between myotube guidance and axon guidance. The association of myotube guidance pathways with developmental disorders is also discussed.

Heterogenic Genetic Background of Distal Arthrogryposis-Review of the Literature and Case Report

Distal arthrogryposis (DA) is a skeletal muscle disorder that is characterized by the presence of joint contractures in various parts of the body, particularly in the distal extremities. In this study, after a systematic review of the literature, we present a case report of a non-consanguineous family. In our case, the first-trimester ultrasound was negative, and the presence of the affected mother was not enough for the parents to consent to us performing invasive amniotic fluid sampling. The second-trimester ultrasound showed clear abnormalities suggestive of arthrogryposis. Whole-exome sequencing was performed and an autosomal dominantly inherited disease-associated gene was identified. In our case, a pathogenic variant in the TNNT3 gene c.188G>A, p.Arg63His variant was identified. The mother, who had bilateral clubfoot and hand involvement in childhood, carried the same variant. The TNNT3 gene is associated with distal arthrogryposis type 2B2, which is characterized by congenital contractures of the distal limb joints and facial dysmorphism. In the ultrasound, prominent clubfoot was identified, and the mother, who also carried the same mutation, had undergone surgeries to correct the clubfoot, but facial dysmorphism was not detected. Our study highlights the importance of proper genetic counseling, especially in an affected parent(s), and close follow-up during pregnancy.

Preoperative Evaluation for Free Functional Muscle Transfer in Upper Extremity Amyoplasia: A Multicenter Report of 3 Cases

CASE

A multicenter series of 3 patients with amyoplasia of the upper extremity were indicated for gracilis free functional muscle transfer (FFMT) to restore elbow flexion and found to have an absent gracilis. A final case is discussed detailing standardized evaluation with ultrasound to confirm gracilis before surgical intervention.

CONCLUSION

In amyoplasia, the gracilis muscle may be absent or have fatty infiltration, making this donor muscle inadequate. Preoperative ultrasound to determine the presence of the gracilis is noninvasive and recommended in patients with amyoplasia of the upper extremity being considered for FFMT.

EVALUATION OF ARTHROGRYPOTIC FOOT TREATMENT: MINIMUM 10 YEARS FOLLOW-UP

Objective

To evaluate patients with arthrogryposis submitted to extensive surgical treatment with a minimum of 10 years of follow-up regarding the clinical and radiological aspects and the quality of life, using the 36-Item Short Form (SF-36) and the Disease-Specific Instrument (DSI).

Methods

A retrospective study selected 33 patients, totaling 64 operated feet.

Results

The mean age of the patients was 17.9 years (12-39 years), and the mean follow-up time was 14.8 years (11-17). Amyoplasia represented 78.7% of syndromic diagnoses. Isolated posteromedial lateral release (PMLR) was performed in 21.8% of the feet, 27.2% of which required additional bone surgery, and about 50 feet (78.1%) were submitted to PMLR, lateral column shortening, and/or talectomy. In total, 46 talectomies were performed (71.8% of the feet), out of which 44 were the first procedure of choice. SF-36 questionnaire was evaluated and showed that 93.9% of the patients did not have restrictive and disabling pain, and the same percentage considered themselves as healthy and had good expectations for the future.

Conclusion

Arthrogrypotic feet are difficult to treat, require many recurrent surgical procedures, and relapses are the rule. Stiffness is a common feature of these feet, and residual deformities were frequent. Level of Evidence IV; Case Series, Therapeutic Studies.

Open reduction for hip dislocation in children with arthrogryposis multiplex congenital: Outcomes of a systematic review

Introduction

The incidence of hip dislocation (HD) in arthrogryposis multiplex congenital ranges from 15 to 30 %. Besides a stable hip, the ambulation potential of an AMC child is also dependent on severity of associated knee and foot deformations. The primary objective of this review is to determine the proportion of ambulators in AMC children treated by open reduction for HD.

Methods

We searched major electronic bibliographic databases for reports on the treatment of HD among AMC children. Based on the surgical approach for open reduction of HD in AMC children, we divided the included studies into groups 1 (Anterior approach open reduction) and 2 (Medial approach open reduction).

Results

We pooled 59 children/94 hips in this review from 7 studies. We identified 45 children/71 hips and 14 children/23 hips with a mean age of 20 (4-64) and 4.5 (0.5-11) months in groups 1 and 2, respectively. There were 97 % (44) and 92 %(Obeidat et al., 2011) 13 ambulators in groups 1 and 2, respectively. 47 % and 36 % of hips in groups 1 and 2 required additional procedures besides open reduction for redislocation and maintenance of hip reduction. 31 %22 and 13 %(Fisher et al., 1970 Feb) 3 of the hips sustained avascular necrosis in group 1 and 2.

Conclusion

Children with AMC associated HD can be expected to ambulate with and without assistance in 90 % of the cases however, the foot and knee problems also need concomitant management. In children less than 6 months of age the medial approach based open reduction may be more efficacious and less complicating than anterior approach based open reduction however, at a later age anterior approach based open reduction is more effective due to need for pelvic and femur sided additional procedures.

Growth Charts for Children With Arthrogryposis Multiplex Congenita

Children with arthrogryposis multiplex congenita (AMC) often demonstrate growth differences compared with typically developing (TD) children. However, growth charts have not been developed for this population. The purpose of this study was to create AMC-specific growth charts and to compare these values to those of TD children. A retrospective review of height/length and weight for 206 children with AMC was performed. Growth charts were developed and stratified over seven percentiles; these were then compared with growth charts of TD children. Children with AMC tend to be smaller in stature and weight compared with TD children, particularly in the first 36 months of life. Thereafter, weight values trend toward the 50th percentile of TD children, but height/length values persist around the 5th percentile of TD children. The development of AMC-specific growth charts provides health care providers an objective tool to evaluate growth patterns of patients with AMC.

Early Diagnosis and Management of Arthrogryposis Multiplex Congenita in a Neonate: A Case Study

Arthrogryposis multiplex congenita (AMC) is a rare condition characterized by multiple joint contractures at birth, affecting two or more body areas. The clinical examination revealed physical abnormalities indicative of AMC, including joint contractures, clubfeet, and scoliosis. The diagnostic evaluation confirmed the clinical suspicion, and prompt management was initiated to address respiratory distress and potential sepsis. Early diagnosis and multidisciplinary care are essential for optimizing outcomes in neonates with AMC. We present the case of a one-day-old neonate who exhibited immediate respiratory distress upon birth and was born via a lower segment cesarean section (LSCS) to a 31-year-old mother. This case underscores the importance of recognizing prenatal ultrasound findings suggestive of AMC and implementing appropriate postnatal care strategies for affected neonates. Early diagnosis and multidisciplinary care are essential for optimizing outcomes in neonates with AMC.

Paediatric syndromic scoliosis: proceedings of the half-day course at the 57th annual meeting of the Scoliosis Research Society

There are some syndromes that present with unique manifestations pertaining to the spinal column. A good working understanding of these common syndromes is useful for the spinal deformity surgeons and related healthcare providers. This review attempts to encompass these unique features and discuss them in three broad groups: hypermobility syndromes, muscle pathology-related syndromes, and syndromes related to poor bone quality. This review explores the features of these syndromes underpinning the aspects of surgical and medical management. This review represents the proceedings of the Paediatric Half-Day Course at the 57th Annual Meeting of the Scoliosis Research Society.

A retrospective study on the correction of distal arthrogryposis with a progressive extension brace

Purpose

Camptodactyly, clasped thumbs, and windblown hands are distinctive features of distal arthrogryposis (DA). Current therapeutic interventions often yield suboptimal effects, predisposing patients to relapses and complications. This study explicates a corrective approach involving a progressive extension brace for the management of DA and evaluates its clinical outcomes.

Methods

Between 2015 and 2023, progressive extension braces were used in 32 DA patients, with an average follow-up of 4.8 years. Patients were stratified by age into four groups: 0-1, 1-3, 3-7, and above 7 years. The correction of camptodactyly was assessed based on the total active movement (TAM) of metacarpophalangeal joints (MPJ) and proximal interphalangeal joints (PIPJ), as well as the extensor lag of PIPJ. Clasped thumb correction was evaluated by measuring the thumb-to-index finger metacarpal angle (M1M2 angle) and the degree of deviation at the first MPJ (M1P1 angle). The quality of life for the children was measured using PedsQL 4.0, while parental satisfaction was gauged using the FACE questionnaire.

Results

Earlier intervention with a progressive extension brace yielded superior corrective results. Infants aged 0-1 year and toddlers aged 1-3 years achieved average TAM scores of 152° and 126° after correction; however, patients older than 3 years experienced a significant decrease in TAM with the same treatment. Infants and toddlers with DA showed improvement in the average extensor lag from 46° to 6°. The M1M2 angle increased from an average of 38° to 65°, with the M1P1 angle decreasing from an average of 43° to 5°. After the treatment, average PedsQL scores of 94.7 (parent-reported) and 89.3 (child-reported) were achieved. Among the 32 parents, 24 expressed high satisfaction, 5 expressed moderate satisfaction, and 3 expressed fair satisfaction.

Conclusion

The early, progressive, and consistent use of an extension brace significantly improved joint mobility and corrected camptodactyly and clasped thumbs. It can be an effective approach to addressing hand deformities in patients with DA.

Functional Independence of Children With Arthrogryposis

BACKGROUND

Arthrogryposis (AMC) is a descriptive term to characterize a child born with multiple joint contractures. Treatment aims to improve functional independence, yet the literature objectively describing functional independence in this population is scarce. This study aimed to describe the functional independence of children with AMC through the lens of the Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT) and observational activities of daily living (ADL) tasks.

METHODS

Patients with AMC between the ages of 3 and 12 years participated in this prospective study. Parents completed the PEDI-CAT while a trained occupational therapist observed children as they completed a checklist of functional ADL tasks. Patients were grouped according to developmental age groups: "preschoolers" (3 to 5 y), "early school-age" (6 to 9 y), and "late school-age" (10 to 12 y). Patient's PEDI-CAT normative scores were described, comparing the study population to typically developing children, and differences in each domain were examined between developmental age groups. The observed ADL tasks completed were also described, and differences in scores were examined between developmental age groups.

RESULTS

Forty-four patients (mean age of 7±2.86 y) were enrolled. The distribution between age groups was nearly even. Mean daily activities T -score for patients with AMC was 25.80±11.98 and the mean mobility T -score was 17.39±9.77. Late school-age children scored significantly lower than preschool-age children in both of these domains ( P <0.01). Observed ADL tasks demonstrated a high level of required assistance for patients (range: 27.3% to 61.4%), although older school-age children did show greater independence with tested activities than preschool-age children ( P =0.05).

CONCLUSION

Children with AMC are significantly limited in functional independence, particularly regarding age-appropriate daily activities and mobility. Outcomes from this study provide a reference to help gauge the results of nonoperative and surgical treatment toward improving functional independence in this population.

LEVEL OF EVIDENCE

Level III: prognostic study.

Homologous mutations in human β, embryonic, and perinatal muscle myosins have divergent effects on molecular power generation

Mutations at a highly conserved homologous residue in three closely related muscle myosins cause three distinct diseases involving muscle defects: R671C in β-cardiac myosin causes hypertrophic cardiomyopathy, R672C and R672H in embryonic skeletal myosin cause Freeman-Sheldon syndrome, and R674Q in perinatal skeletal myosin causes trismus-pseudocamptodactyly syndrome. It is not known whether their effects at the molecular level are similar to one another or correlate with disease phenotype and severity. To this end, we investigated the effects of the homologous mutations on key factors of molecular power production using recombinantly expressed human β, embryonic, and perinatal myosin subfragment-1. We found large effects in the developmental myosins but minimal effects in β myosin, and magnitude of changes correlated partially with clinical severity. The mutations in the developmental myosins dramatically decreased the step size and load-sensitive actin-detachment rate of single molecules measured by optical tweezers, in addition to decreasing overall enzymatic (ATPase) cycle rate. In contrast, the only measured effect of R671C in β myosin was a larger step size. Our measurements of step size and bound times predicted velocities consistent with those measured in an in vitro motility assay. Finally, molecular dynamics simulations predicted that the arginine to cysteine mutation in embryonic, but not β, myosin may reduce pre-powerstroke lever arm priming and ADP pocket opening, providing a possible structural mechanism consistent with the experimental observations. This paper presents direct comparisons of homologous mutations in several different myosin isoforms, whose divergent functional effects are a testament to myosin's highly allosteric nature.

Arthrogryposis multiplex congenita: dental and maxillofacial phenotype - A scoping review

INTRODUCTION

Arthrogryposis multiplex congenita (AMC) is a heterogeneous group of disorders associated with decreased fetal movement, with a prevalence between 1/3000 and 1/5200 live births. Typical features of AMC include multiple joint contractures present at birth, and can affect all joints of the body, from the jaw, and involving the upper limbs, lower limbs and spine. The jaws may be affected in 25 % of individuals with AMC, with limited jaw movement and mouth opening. Other oral and maxillofacial deformities may be present in AMC, including cleft palate, micrognathia, periodontitis and delayed teething. To our knowledge, oral and maxillofacial abnormalities have not been systematically assessed in individuals with AMC. Therefore, this scoping review was conducted to identify, collect, and describe a comprehensive map of the existing knowledge on dental and maxillofacial involvement in individuals with AMC.

METHODOLOGY

A scoping review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines. The PRISMA guidelines for scoping reviews were followed and databases were searched for empirical articles in English and French published until October 2022. We searched MEDLINE, Embase, Web of Science and ERIC databases. Two authors independently reviewed the articles and extracted the data.

RESULTS

Of a total of 997 studies that were identified, 96 met the inclusion criteria and were subsequently included in this scoping review. These 96 studies collectively provided insights into 167 patients who exhibited some form of oral and/or maxillofacial involvement. Notably, 25 % of these patients were within the age range of 0-6 months. It is worth highlighting that only 22 out of the 96 studies (22.9 %), had the primary objective of evaluating dental and/or maxillofacial deformities. Among the patients studied, a prevalent pattern emerged, revealing that severe anomalies such as micrognathia (56 %), high-arched palate (29 %), cleft palate (40 %), limited mouth opening (31 %), and dental anomalies (28 %) were frequently observed. Importantly, many of these patients were found to have more than one of these anomalies. Even though these maxillofacial impairments are known to be associated with dental problems (e.g., cleft palate is associated with oligodontia, hypodontia, and malocclusion), their secondary effects on the dental phenotype were not reported in the studies.

CONCLUSION

Our findings have uncovered a notable deficiency in existing literature concerning dental and maxillofacial manifestations in AMC. This underscores the need for interdisciplinary collaboration and the undertaking of extensive prospective cohort studies focused on AMC. These studies should assess the oral and maxillofacial abnormalities that can impact daily functioning and overall quality of life.

[Nerve Transfers in Children with Non-traumatic Amyoplasia]

BACKGROUND

The treatment of obstetric brachial plexus palsy through primary reconstruction and nerve transfers has been established in the past decades. In the case of non-traumatic diseases that lead to flaccid paralysis and the inability to move the extremities, such as transverse myelitis (TM) or arthrogryposis multiplex congenita (AMC), which can have a wide variety of causes, the focus has been on rehabilitative therapy so far, while surgical interventions have been used to a lesser extent, e. g., in the form of osteotomies or muscle transfers. Our aim is to establish nerve transfers as a surgical option to improve mobility in non-traumatic amyoplasia.

PATIENTS

This work presents the needs-adapted treatment of a total of 23 patients (aged 4 months to 64 months, 18 with AMC and 5 with TM) using nerve transfers on the upper extremity.

RESULTS

We were able to show that early nerve transfers in the upper extremity enabled the reanimation of muscles in both AMC and TM.

CONCLUSION

This work shows that the treatment of non-traumatic amyoplasia in children with selective nerve grafts is a successful method. Nerve transfers allow patients to gain or regain important functions for managing independent everyday life. The surgical methods have been established in the treatment of traumatic nerve injuries. They are well-known and can be carried out safely. We believe that this is an important treatment option for paediatric patients with paralysis associated with TM or AMC, which should also be known to the treating physicians.

Effectiveness of the Ponseti method for congenital clubfoot in patients with arthrogryposis: A systematic review and meta-analysis of observational studies

Purpose

The aim of this systematic review was to address the Ponseti method in arthrogrypotic clubfoot treatment and evaluate the success, complication, and recurrence rates.

Method

A systematic review was performed in the PubMed, Scopus, Embase, and Web of Science databases on 9 January 2023, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Success, recurrence, and complication rates were evaluated and analyzed. Risks of bias and the quality of the studies were also evaluated.

Results

Five case series, including 53 patients (102 feet), were identified. According to this model, the initial success rate was 91% (95% confidence interval = 0.79-0.96) with I2 = 43%, and the final success was 68% (at 5.8 years of follow-up). Recurrence rate was 30% (95% confidence interval = 0.14-0.52).

Conclusion

Ponseti method is indicated in the initial treatment of arthrogrypotic clubfeet, as it is a minimally invasive method with a high correction rate (91%). However, a high recurrence rate (30%) requires early detection and adequate treatment.

Level of evidence

Level III.

PROSPERO Protocol

CRD42020210373.

A Study of Polish Family with Scoliosis and Limb Contractures Expands the MYH3 Disease Spectrum

A disease associated with malfunction of the MYH3 gene is characterised by scoliosis, contractures of the V fingers, knees and elbows, dysplasia of the calf muscles, foot deformity and limb length asymmetry. The aim of this study was to identify the cause of musculoskeletal deformities in a three-generation Polish family by exome sequencing. The segregation of the newly described c.866A>C variant of the MYH3 gene in the family indicates an autosomal dominant model of inheritance. The detected MYH3 variant segregates the disease within the family. The presented results expand the MYH3 disease spectrum and emphasize the clinical diagnostic challenge in syndromes harbouring congenital spine defects and joint contractures.

Physical therapy of temporomandibular disorder in a child with arthrogryposis multiplex congenita: A case report and literature review

BACKGROUND

Arthrogryposis multiplex congenita (AMC) is a rare congenital disorder characterized by the occurrence of polyarticular contractures. Temporomandibular disorders (TMD) affect 25% of patients with arthrogryposis.

CLINICAL PRESENTATION

In this case report, the authors describe rehabilitation of a child between 8 and 24 months of age with AMC accompanied by Pierre-Robin Sequence. Physiotherapy directed to the TMJ included manual therapy, food intake training, and sensory training.

CONCLUSION

Increase in the mobility of the TMJ and improvement in food intake, swallowing, speech, and breathing were achieved. Further research is necessary for investigating the effects of the proposed protocol of physiotherapy on a larger number of children with AMC and co-occurrence of TMD.

Survival in Mudejar Spain in the Middle Ages (thirteenth-fourteenth centuries): Ancient Rare Diseases-an uncommon diagnosis in archaeological human remains

PURPOSE

The finding of severe skeletal alterations in ancient remains could give us useful information not only about the pathologies of the individual per se, as it could infer the state of health of a population.

METHODS

From the findings of the Mudéjar Cemetery of Uceda (Guadalajara, Central Spain) where a total of 116 burials with almost complete skeleton were recovered, an interesting individual is presented (palaeopathological perspective). The individual 114UC corresponds to a male of 20-25 years old and its age goes back to the thirteenth-fourteenth centuries.

RESULTS

The first inspection showed the presence of serious alterations especially in the lumbar spine and pelvic girdle. Seven vertebrae (from T11 to L5) showed an unusual posterior fusion only in the postzygapophyseal joints. The pelvis, after being accurately assembled and congruence verified by X-ray and CT scan, showed a noticeable asymmetry of both iliac wings together with a coxa magna protusa (Otto's pelvis), severe anteversion of both cup hips and osteochondritis of the right femoral head. The posterior-slope of both tibias reached about 10°.

CONCLUSIONS

The differential diagnoses lead us to think of Arthrogryposis Multiplex Congenita as the most probable diagnosis. We analyzed the same biomechanical aspects after taking into account some patterns that give us information about a possible mobility in the first stage of life. We discuss the very few other cases described both from artworks and in the palaeopathological record. To our knowledge, this case could be the oldest published case of AMC worldwide.

Spinal Fusion in Patients With Classic Amyoplasia and General Arthrogryposis

BACKGROUND

Arthrogryposis multiplex congenita is a group of conditions characterized by joint contractures affecting 2 or more joints. This study describes results of spinal fusion in patients with classic amyoplasia and general arthrogryposis.

METHODS

IRB approved retrospective review of patients with a diagnosis of classic amyoplasia and general arthrogryposis who had a primary definitive posterior spinal fusion between 1990 and 2017 at a single pediatric institution. Patients with distal and syndromic arthrogryposis were excluded as well as patients treated with growth-sparing spinal instrumentation. The Modified Clavien-Dindo-sink (MCDS) classification system was used to describe postoperative complications.

RESULTS

Over the 28-year period, 342 patients were diagnosed with amyoplasia and general arthrogryposis. Among the 342 patients, 60 (18%) had scoliosis, and 22 (6% of the cohort and 37% of those with scoliosis) were treated surgically. Six patients had growth-sparing techniques, initial fusion elsewhere, or ˂1 year of follow-up, leaving 15 patients. Of the 15, 9 (60%) had a posterior spinal fusion (PSF) and 6 (40%) had a combined anterior spinal fusion (ASF)/PSF. The ASF/PSF group was significantly younger at surgery, had a greater American Society of Anesthesiologists status, longer surgery duration, and lower implant density. The average preoperative major coronal deformity in ASF/PSF patients (108 degrees) was greater than patients treated with PSF alone (88 deg). There were 11 complications in 7 patients, with the most common being deep infection requiring reoperation (5/11, 45%). There was 1 instance (1/11, 9%) of each: prolonged intensive care unit admission (>72 h), superficial wound dehiscence, symptomatic implants requiring removal/revision, coronal plane progression requiring extension of fusion, recurrent pneumothorax requiring return to OR, and pseudoarthrosis leading to implant failure (without revision). Complications occurred in 1/9 (11%) PSF-only patients and 6/6 (100%) ASF/PSF patients with all 6 ASF/PSF patients requiring at least 1 reoperation. The average coronal correction was 48% in the PSF-only group and 28% in the ASF/PSF group.

CONCLUSION

Complication rates after spinal fusion for scoliosis in arthrogryposis multiplex congenita patients are high, especially in patients undergoing ASF/PSF, deep infection is common, and major coronal plane curve correction is modest.

LEVEL OF EVIDENCE

II Retrospective Study.

A rare case of arthrogryposis multiplex congenita in a 2-year-old boy case report

Arthrogryposis multiplex congenita (AMC) is an uncommon condition present from birth that is marked by a combination of weakened muscles and multiple joint contractures. We present a case of a 2-year-old boy with AMC, who was born to consanguineous parents in Saudi Arabia. He presented with musculoskeletal abnormalities of all four limbs, including symmetric contractures in multiple joints of the body, bilateral developmental dysplasia of the hip, and vertical talus. Dysmorphic features included low-set ears, chin recession, triangular face, and nevus flammeus on the face. The child also had lactose intolerance, gastritis, inguinal hernia, and right-sided undescended testis. Surgical interventions were planned after a multidisciplinary team discussion. This case report highlights the good prognosis of AMC with all four-limb involvement and the importance of a thorough physical examination and a multidisciplinary approach to the diagnosis and management of AMC.

Congenital vertical talus deformity in children with distal arthrogryposis: good clinical outcomes despite high rate of residual radiographic deformity

Patients with a diagnosis of arthrogryposis often present with various orthopedic conditions, one of which is congenital vertical talus (CVT). This is the first study of this specific subset of syndromic patients to evaluate the medium-term outcomes of CVT correction using the minimally invasive Dobbs method. All patients with vertical talus and distal arthrogryposis who received treatment at our institution between January 2006 and June 2021 were identified. Radiographs, clinical notes and Patient-Reported Outcome Measurement Information System (PROMIS) scores (when available) were retrospectively reviewed. An alpha of 0.05 was used for all statistical analyses. In total 12 patients (19 feet) met all inclusion criteria and were included in the final analysis. By the time of the most recent visit, the average lateral Talar-Axis First Metatarsal Base Angle of the entire cohort increased from 13.73 ± 9.75 degrees 2 weeks postoperatively to 28.75 ± 23.73 degrees ( P  = 0.0076). Radiographic recurrence of the talonavicular deformity was seen in nine feet (47.4%), 4 (21.1%) of which required additional unplanned surgery, The average PROMIS scores of the entire cohort in the pain interference, mobility and peer relationship domains were 48.97 ± 9.56, 47.9 ± 11.60 and 52.87 ± 8.31, respectively. Despite a higher radiographic recurrence rate of talonavicular deformity in this specific subset of syndromic patients, these patients still report PROMIS scores near the population average in the pain interference, mobility and peer relationships domains. We believe that the minimally invasive Dobbs method should be recommended as the first-line treatment method for these patients. Level of evidence: Level III.

Features of Congenital Arthrogryposis Due to Abnormalities in Collagen Homeostasis, a Scoping Review

Congenital arthrogryposis (CA) refers to the presence of multiple contractures at birth. It is a feature of several inherited syndromes, notable amongst them are disorders of collagen formation. This review aims to characterize disorders that directly or indirectly impact collagen structure and function leading to CA in search for common phenotypic or pathophysiological features, possible genotype-phenotype correlation, and potential novel treatment approaches based on a better understanding of the underlying pathomechanism. Nine genes, corresponding to five clinical phenotypes, were identified after a literature search. The most notable trend was the extreme phenotype variability. Clinical features across all syndromes ranged from subtle with minimal congenital contractures, to severe with multiple congenital contractures and extra-articular features including skin, respiratory, or other manifestations. Five of the identified genes were involved in the function of the Lysyl Hydroxylase 2 or 3 enzymes, which enable the hydroxylation and/or glycosylation of lysyl residues to allow the formation of the collagen superstructure. Whilst current treatment approaches are post-natal surgical correction, there are also potential in-utero therapies being developed. Cyclosporin A showed promise in treating collagen VI disorders although there is an associated risk of immunosuppression. The treatments that could be in the clinical trials soon are the splice correction therapies in collagen VI-related disorders.

Homologous mutations in β, embryonic, and perinatal muscle myosins have divergent effects on molecular power generation

Mutations at a highly conserved homologous residue in three closely related muscle myosins cause three distinct diseases involving muscle defects: R671C in β -cardiac myosin causes hypertrophic cardiomyopathy, R672C and R672H in embryonic skeletal myosin cause Freeman Sheldon syndrome, and R674Q in perinatal skeletal myosin causes trismus-pseudocamptodactyly syndrome. It is not known if their effects at the molecular level are similar to one another or correlate with disease phenotype and severity. To this end, we investigated the effects of the homologous mutations on key factors of molecular power production using recombinantly expressed human β , embryonic, and perinatal myosin subfragment-1. We found large effects in the developmental myosins, with the most dramatic in perinatal, but minimal effects in β myosin, and magnitude of changes correlated partially with clinical severity. The mutations in the developmental myosins dramatically decreased the step size and load-sensitive actin-detachment rate of single molecules measured by optical tweezers, in addition to decreasing ATPase cycle rate. In contrast, the only measured effect of R671C in β myosin was a larger step size. Our measurements of step size and bound times predicted velocities consistent with those measured in an in vitro motility assay. Finally, molecular dynamics simulations predicted that the arginine to cysteine mutation in embryonic, but not β , myosin may reduce pre-powerstroke lever arm priming and ADP pocket opening, providing a possible structural mechanism consistent with the experimental observations. This paper presents the first direct comparisons of homologous mutations in several different myosin isoforms, whose divergent functional effects are yet another testament to myosin's highly allosteric nature.

Fetal arthrogryposis-what do we tell the prospective parents?

Arthrogryposis, also termed arthrogryposis multiplex congenita, is a descriptive term for conditions with multiple congenital contractures (MCC). The etiology is extremely heterogeneous. More than 400 specific disorders have been identified so far, which may lead to or are associated with MCC and/or fetal hypo- and akinesia as a clinical sign. With improved sensitivity of prenatal ultrasound and expanding prenatal diagnostic options, clinicians are tasked with providing early detection in order to counsel the prospective parents regarding further prenatal diagnostic as well as management options. We summarize the most important knowledge to raise awareness for early detection in pregnancy. We review essential points for counseling when MCC is detected in order to provide answers to common questions, which, however, cannot replace interdisciplinary expert opinion in the individual case.

Distal arthrogryposis in a girl arising from a novel TNNI2 variant inherited from paternal somatic mosaicism

TNNI2 at 11p15.5 encodes troponin I2, fast skeletal type, which is a member of the troponin I gene family and a component of the troponin complex. Distal arthrogryposis (DA) is characterized by congenital limb contractures without primary neurological or muscular effects. DA is inherited in an autosomal dominant fashion and is clinically and genetically heterogeneous. Exome sequencing identified a causative variant in TNNI2 [NM_003282.4:c.532T>C p.(Phe178Leu)] in a Japanese girl with typical DA2b. Interestingly, the familial study using Sanger sequencing suggested a mosaic variant in her healthy father. Subsequent targeted amplicon-based deep sequencing detected the TNNI2 variant with variant allele frequencies of 9.4-17.7% in genomic DNA derived from peripheral blood leukocytes, saliva, hair, and nails in the father. We confirmed a disease-causing variant in TNNI2 in the proband inherited from her asymptomatic father with its somatic variant. Our case demonstrates that careful clinical and genetic evaluation is required in DA.

Electromyography in Congenital Zika Syndrome

INTRODUCTION

Congenital Zika virus syndrome is a distinct pattern of birth defects in fetuses infected by the Zika virus. It presents a broad clinical spectrum that includes occurrences of microcephaly, hypertonia, dysphagia, hyperexcitability, seizures, and arthrogryposis. Imaging findings show neuronal migration disorders.

METHODOLOGY

Case reports have suggested that arthrogryposis has a neurogenic cause. We analyzed needle electromyography and nerve conduction examinations on 77 patients aged 2-24 months presenting highly probable congenital Zika virus syndrome, with or without arthrogryposis.

RESULTS

All those with arthrogryposis presented with chronic muscle denervation in the electromyography examination. Similarly, children with single or reversible joint abnormalities at birth showed the same findings. Denervation in the paravertebral musculature was found in all of the children with diaphragmatic paralysis or thoracic deformities.

CONCLUSIONS

We propose that congenital contractures associated with congenital Zika virus syndrome are caused by the malformation of upper and lower motor neurons during embryogenesis.

Effectiveness of Ponseti technique in management of arthrogrypotic clubfeet - a prospective study

BACKGROUND

Clubfoot constitutes roughly 70 percent of all foot deformities in arthrogryposis syndrome and 98% of those in classic arthrogryposis. Treatment of arthrogrypotic clubfoot is difficult and challenging due to a combination of factors like stiffness of ankle-foot complex, severe deformities and resistance to conventional treatment, frequent relapses and the challenge is further compounded by presence of associated hip and knee contractures.

METHOD

A prospective clinical study was conducted using a sample of nineteen clubfeet in twelve arthrogrypotic children. During weekly visits Pirani and Dimeglio scores were assigned to each foot followed by manipulation and serial cast application according to the classical Ponseti technique. Mean initial Pirani score and Dimeglio score were 5.23 ± 0.5 and 15.79 ± 2.4 respectively. Mean Pirani and Dimeglio score at last follow up were 2.37 ± 1.9 and 8.26 ± 4.93 respectively. An average of 11.3 casts was required to achieve correction. Tendoachilles tenotomy was required in all 19 AMC clubfeet.

RESULT

The primary outcome measure was to evaluate the role of Ponseti technique in management of arthrogrypotic clubfeet. The secondary outcome measure was to study the possible causes of relapses and complications with additional procedures required to manage clubfeet in AMC an initial correction was achieved in 13 out of 19 arthrogrypotic clubfeet (68.4%). Relapse occurred in 8 out of 19 clubfeet. Five of those relapsed feet were corrected by re-casting ± tenotomy. 52.6% of arthrogrypotic clubfeet were successfully treated by the Ponseti technique in our study. Three patients failed to respond to Ponseti technique required some form of soft tissue surgery.

CONCLUSION

Based on our results, we recommend the Ponseti technique as the first line initial treatment for arthrogrypotic clubfeet. Although such feet require a higher number of plaster casts with a higher rate of tendo-achilles tenotomy but the eventual outcome is satisfactory. Although, relapses are higher than classical idiopathic clubfeet, most of them respond to re-manipulation and serial casting ± re-tenotomy.

Lethal respiratory course and additional features expand the phenotypic spectrum of PIEZO2-related distal arthrogryposis type 5

Distal arthrogryposes (DA) are a group of conditions presenting with multiple congenital contractures in the distal joints. The 10 types of DA are distinguished by different extra-articular manifestations. Heterozygous gain-of-function variants in PIEZO2 are known to cause a spectrum of DA conditions including DA type 3, DA type 5, and possibly Marden Walker syndrome, which are usually distinguished by the presence of cleft palate (DA3), ptosis and restriction in eye movements (DA5), and specific facial abnormalities and central nervous system involvement, respectively. We report on a boy with a recurrent de novo heterozygous PIEZO2 variant in exon 20 (NM_022068.3: c.2994G > A, p.(Met998Ile); NM_001378183.1: c.3069G > A, p.(Met1023Ile)), who presented at birth with DA and later developed respiratory insufficiency. His phenotype broadly fits the PIEZO2 phenotypic spectrum and potentially extends it with novel phenotypic features of pretibial linear vertical crease, immobile skin, immobile tongue, and lipid myopathy.

Long term ophthalmic complications of distal arthrogryposis type 5D

BACKGROUND

Distal Arthrogryposis type 5D (DA5D) is a rare genetic disease, expressed phenotypically by skeletal and ocular abnormalities.

MATERIALS AND METHODS

Two sisters, ages 42 and 46 years old, were ascertained, both diagnosed with arthrogryposis and unusual ophthalmic late expressions of the disease. They were examined and followed up by both ophthalmologists and medical geneticists. Molecular analysis was performed and population screening followed among healthy individuals of the same ethnic background who reside in the same village.

RESULTS

The two sisters expressed myogenic ptosis with poor levator palpebrae function, limitation in up gaze, lagophthalmos, refractive errors, corneal scarring and vascularization along with severe distal arthrogryposis. The newly reported features were: significant lower lid retraction, causing inferior scleral show. Sanger sequencing of the coding regions of ECEL1 gene revealed a homozygous deletion of 46 bps. The carrier frequency is 1:24 (4.2% carriers) in the probands' village.

CONCLUSIONS

We diagnosed two patients with DA5D carrying a homozygous pathogenic genetic variant previously reported only once. We report the late ophthalmologic manifestations of this rare disorder and emphasize the importance to recognize possible long-term ophthalmic complications. Measures are needed to diagnose this rare disorder at a younger age and to address ophthalmic and orthopedic complications that might be prevented. We revealed the causative genetic variant and a carrier frequency of 1:24 for DA5D, in the probands' village, thus enabling accurate genetic counselling and justifying genetic testing to the residents of this village as a diagnostic and preventive measure.

An Unusual Combination of Arthrogryposis, Gastroschisis, Cecal Volvulus, and Malignant Hyperthermia in a Young Woman: A Case Report

BACKGROUND The purpose of this study is to discuss a patient with a history of conditions, including arthrogryposis, gastroschisis, and malignant hyperthermia, who presented with cecal volvulus requiring urgent surgical intervention. CASE REPORT A 29-year-old woman with a history of arthrogryposis, gastroschisis, malignant hyperthermia, and multiple childhood abdominal surgeries presents to the Emergency Department (ED) with 2 days of abdominal pain and bloody diarrhea. A CT abdomen/pelvis revealed findings concerning for a cecal volvulus. The patient was premedicated and monitored closely by the anesthesia team due to her history of malignant hyperthermia. She underwent an exploratory laparotomy, where a dilated cecum and proximal ascending colon were found to be completely volvulized around the mesentery. Manual bowel detorsion was performed, which resulted in reperfusion of the ischemic-appearing bowel, which then appeared viable. She recovered well after the procedure and was discharged on postoperative day 5. CONCLUSIONS This case highlights a patient who presented with a combination of 4 findings: arthrogryposis, gastroschisis, malignant hyperthermia, and cecal volvulus. With arthrogryposis reported to be associated with gastroschisis and malignant hyperthermia, this report not only corroborates this association, but also aims to draw attention to the fact that these conditions have potential to occur jointly with cecal volvulus. Given the patient's history of gastroschisis requiring extensive abdominal surgeries that contribute as risk factors for cecal volvulus, it is possible there may be other arthrogryposis patients who present with cecal volvulus similar to that seen in this patient.

Excessive mechanotransduction in sensory neurons causes joint contractures

Distal arthrogryposis (DA) is a collection of rare disorders that are characterized by congenital joint contractures. Most DA mutations are in muscle- and joint-related genes, and the anatomical defects originate cell-autonomously within the musculoskeletal system. However, gain-of-function mutations in PIEZO2, a principal mechanosensor in somatosensation, cause DA subtype 5 (DA5) through unknown mechanisms. We show that expression of a gain-of-function PIEZO2 mutation in proprioceptive sensory neurons that mainly innervate muscle spindles and tendons is sufficient to induce DA5-like phenotypes in mice. Overactive PIEZO2 causes anatomical defects through increased activity within the peripheral nervous system during postnatal development. Furthermore, botulinum toxin (Botox) and a dietary fatty acid that modulates PIEZO2 activity reduce DA5-like deficits. This reveals a role for somatosensory neurons: Excessive mechanosensation within these neurons disrupts musculoskeletal development.

Novel variants of NEK9 associated with neonatal arthrogryposis: Two case reports and a literature review

Objective: Pathogenic variants in NEK9 (MIM: 609798) have been identified in patients with lethal congenital contracture syndrome 10 (OMIM: 617022) and arthrogryposis, Perthes disease, and upward gaze palsy (APUG and OMIM: 614262). The shared core phenotype is multiple joint contractures or arthrogryposis. In the present study, three novel variants of NEK9 associated with neonatal arthrogryposis were reported. Methods: The clinical data of two premature infants and their parents were collected. The genomic DNA was extracted from their peripheral blood samples and subjected to trio-whole-exome sequencing (trio-WES) and copy number variation analysis. Results: Using trio-WES, a total of three novel pathogenic variants of NEK9 were detected in the two families. Patient 1 carried compound heterozygous variations of c.717C > A (p. C239*741) and c.2824delA (p.M942Cfs*21), which were inherited from his father and mother, respectively. Patient 2 also carried compound heterozygous variations of c.61G > T (p. E21*959) and c. 2824delA (p. M942Cfs*21), which were inherited from his father and mother, respectively. These variants have not been previously reported in the ClinVar, HGMD, or gnomAD databases. Conclusion: This is the first report about NEK9-related arthrogryposis in neonatal patients. The findings from this study suggest that different types of mutations in NEK9 lead to different phenotypes. Our study expanded the clinical phenotype spectrum and gene spectrum of NEK9-associated arthrogryposis.

Talectomy for arthrogrypotic foot deformities: A systematic review

BACKGROUND

Arthrogryposis multiplex congenita (AMC) is one of the most common congenital joint contracture syndromes. Talectomy has been proposed for severe foot deformities in AMC, but the literature is limited. The purpose of this systematic review is to evaluate the indications, outcomes and complications of talectomy in arthrogrypotic foot deformities.

METHODS

The articles were found through Embase and Medline. Screening was conducted by two independent investigators with disagreements resolved by a third reviewer. Relevant data regarding demographics, outcomes and complications were collected.

RESULTS

Of 232 feet, 71.98 % and 62.22 % had clinical and radiographic improvements respectively. Amongst 122 patients, 92.62 % could ambulate following surgery. Recurrent deformities and revision surgery were seen in 16.81 % and 13.36 % of cases respectively.

CONCLUSIONS

Talectomy is a valid surgical option for severe arthrogrypotic foot deformities with favorable post-operative outcomes and low complication rate.

Diagnostic workup in children with arthrogryposis: description of practices from a single reference centre, comparison with literature and suggestion of recommendations

INTRODUCTION

Arthrogryposis multiplex congenita (AMC) refers to a clinical presentation of congenital contractures involving two or more body areas. More than 400 distinct conditions may lead to AMC, making the aetiological diagnosis challenging. The objective of this work was to set up evidence-based recommendations for the diagnosis of AMC by taking advantage of both data from our nation-wide cohort of children with AMC and from the literature.

MATERIAL AND METHODS

We conducted a retrospective single-centre observational study. Patients had been evaluated at least once at a paediatric age in the AMC clinic of Grenoble University Hospital between 2007 and 2019. After gathering data about their diagnostic procedure, a literature review was performed for each paraclinical investigation to discuss their relevance.

RESULTS

One hundred and twenty-five patients were included, 43% had Amyoplasia, 27% had distal arthrogryposis and 30% had other forms. A definitive aetiological diagnosis was available for 66% of cases. We recommend a two-time diagnostic process: first, non-invasive investigations that aim at classifying patients into one of the three groups, and second, selected investigations targeting a subset of patients.

CONCLUSION

The aetiological management for patients with AMC remains arduous. This process will be facilitated by the increasing use of next-generation sequencing combined with detailed phenotyping. Invasive investigations should be avoided because of their limited yield.

Relaxin in fibrotic ligament diseases: Its regulatory role and mechanism

Fibrotic ligament diseases (FLDs) are diseases caused by the pathological accumulation of periarticular fibrotic tissue, leading to functional disability around joint and poor life quality. Relaxin (RLX) has been reported to be involved in the development of fibrotic lung and liver diseases. Previous studies have shown that RLX can block pro-fibrotic process by reducing the excess extracellular matrix (ECM) formation and accelerating collagen degradation in vitro and in vivo. Recent studies have shown that RLX can attenuate connective tissue fibrosis by suppressing TGF-β/Smads signaling pathways to inhibit the activation of myofibroblasts. However, the specific roles and mechanisms of RLX in FLDs remain unclear. Therefore, in this review, we confirmed the protective effect of RLX in FLDs and summarized its mechanism including cells, key cytokines and signaling pathways involved. In this article, we outline the potential therapeutic role of RLX and look forward to the application of RLX in the clinical translation of FLDs.

Osseous Ilio-Trochanteric Bars as an Etiology of Hip Contracture in a Child with Congenital Contractures: A Case Report

CASE

A 5-month-old female patient presented with bilateral lower-limb deformities. Hips were fixed at 100° abduction, 15° flexion and 45° external rotation, flexion contracture in the knees, and bilateral teratologic equinovarus deformities. Radiographs revealed ilio-trochanteric osseous bars as the etiology of hip contractures. Staged surgeries were undertaken. At 4 years of age, she could stand upright with orthoses and sit without support.

CONCLUSION

This is the first study to report bilateral congenital ilio-trochanteric osseous bars, which were resected without recurrence. Even with a very low potential of walking, release of the contractures allows for better function and possible wheelchair-dependent mobility in the future.

Biallelic variants in ADAMTS15 cause a novel form of distal arthrogryposis

PURPOSE

We aimed to identify the underlying genetic cause for a novel form of distal arthrogryposis.

METHODS

Rare variant family-based genomics, exome sequencing, and disease-specific panel sequencing were used to detect ADAMTS15 variants in affected individuals. Adamts15 expression was analyzed at the single-cell level during murine embryogenesis. Expression patterns were characterized using in situ hybridization and RNAscope.

RESULTS

We identified homozygous rare variant alleles of ADAMTS15 in 5 affected individuals from 4 unrelated consanguineous families presenting with congenital flexion contractures of the interphalangeal joints and hypoplastic or absent palmar creases. Radiographic investigations showed physiological interphalangeal joint morphology. Additional features included knee, Achilles tendon, and toe contractures, spinal stiffness, scoliosis, and orthodontic abnormalities. Analysis of mouse whole-embryo single-cell sequencing data revealed a tightly regulated Adamts15 expression in the limb mesenchyme between embryonic stages E11.5 and E15.0. A perimuscular and peritendinous expression was evident in in situ hybridization in the developing mouse limb. In accordance, RNAscope analysis detected a significant coexpression with Osr1, but not with markers for skeletal muscle or joint formation.

CONCLUSION

In aggregate, our findings provide evidence that rare biallelic recessive trait variants in ADAMTS15 cause a novel autosomal recessive connective tissue disorder, resulting in a distal arthrogryposis syndrome.

Combining Gene Mutation with Expression of Candidate Genes to Improve Diagnosis of Escobar Syndrome

Escobar syndrome is a rare, autosomal recessive disorder that affects the musculoskeletal system and the skin. Mutations in the CHRNG and TPM2 genes are associated with this pathology. In this study, we conducted a clinical and genetic investigation of five patients and also explored via in silico and gene expression analysis their phenotypic variability. In detail, we identified a patient with a novel composite heterozygous variant of the CHRNG gene and two recurrent mutations in both CHRNG and TPM2 in the rest of the patients. As for the clinical particularities, we reported a list of modifier genes in a patient suffering from myopathy. Moreover, we identified decreased expression of IGF-1, which could be related to the short stature of Escobar patients, and increased expression of POLG1 specific to patients with TPM2 mutation. Through this study, we identified the genetic spectrum of Escobar syndrome in the Tunisian population, which will allow setting up genetic counseling and prenatal diagnosis for families at risk. In addition, we highlighted relevant biomarkers that could differentiate between patients with different genetic defects.

A TNNI2 variant c.525G>T causes distal arthrogryposis in a Chinese family

BACKGROUND

Distal arthrogryposis (DA) is a group of congenital autosomal-dominant disorders secondary to defects in joint and muscle function, characterized by multiple joint contractures of the hands and feet. DA can be divided into 10 types according to clinical features. DA has been confirmed to be caused by mutations in genes encoding components of the contractile apparatus of skeletal muscle fibers, such as troponin I2 (TNNI2).

METHODS

In this study, we report a three-generation DA family belonging to the DA2B type. The clinical characteristics of affected members are genetically stable and consistent, with severe deformities in hands and feet, and two affected adults had short stature. None exhibited facial abnormalities. Blood from three affected and three healthy members were collected for whole-exome sequencing and Sanger sequencing.

RESULTS

A missense variant in TNNI2 (NM_003282.4: c.525G>T: p.K175N) was successfully identified, which resulted in the substitution of amino acid at position 175 of TNNI2 from lysine to asparagines.

CONCLUSION

The variant c.525G>T in TNNI2 explains the cause of DA in the family. This variant was identified in Chinese people for the first time, and the same variant had been reported in another study but no description of clinical symptoms. Our study comprehensively characterized the c.525G>T variant in TNNI2.

TTN as a candidate gene for distal arthrogryposis type 10 pathogenesis

Background

Arthrogryposis is a medical term used to describe congenital contractures which often affect multiple limbs. Distal arthrogryposis (DA) is one of the major categories of arthrogryposis that primarily affects the distal parts of the body, i.e., the hands and the legs. Although ten different types and several subtypes of DAs have been described, the genes associated with each of these DAs are yet to be characterized. Distal arthrogryposis type 10 (DA10) is a rare genetic disease, which is distinguished from the other arthrogryposis types by plantar flexion contractures resulting in toe-walking during infancy as well as variability in contractures of the hip, hamstring, elbow, wrist and finger joints with no ocular or neurological abnormalities. Symptoms of DA10 indicate impairment specifically in the musculoskeletal system. DA10 is still poorly studied.

Aim

The objective of this study was to identify the candidate gene for DA10 by scrutinizing the protein-protein interaction (PPI) networks using in silico tools.

Results

Among the genes that reside within the previously reported genomic coordinates (human chromosome assembly 38 or GRCh38 coordinates 2:179,700,000–188,500,000) of the causative agent of DA10, only TTN (the gene that codes for the protein Titin or TTN) follows the expression pattern similar to the other known DA associated genes and its expression is predominant in the skeletal and heart muscles. Titin also participates in biological pathways and processes relevant to arthrogryposes. TTN-related known skeletal muscle disorders follow the autosomal-dominant pattern of inheritance, which is a common characteristic of distal arthrogryposes as well.

Conclusion

Based on the findings of the analyses and their correlation with previous reports, TTN appears to be the candidate gene for DA10. Our attempt to discover a potential candidate gene may eventually lead to an understanding of disease mechanism and possible treatment strategies, as well as demonstrate the suitability of PPI in the search for candidate genes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00405-5.

Management of arthrofibrosis in neuromuscular disorders: a review

Arthrofibrosis, or rigid contracture of major articular joints, is a significant morbidity of many neurodegenerative disorders. The pathogenesis depends on the mechanism and severity of the precipitating neuromuscular disorder. Most neuromuscular disorders, whether spastic or hypotonic, culminate in decreased joint range of motion. Limited range of motion precipitates a cascade of pathophysiological changes in the muscle-tendon unit, the joint capsule, and the articular cartilage. Resulting joint contractures limit functional mobility, posing both physical and psychosocial burdens to patients, economic burdens on the healthcare system, and lost productivity to society. This article reviews the pathophysiology of arthrofibrosis in the setting of neuromuscular disorders. We describe current non-surgical and surgical interventions for treating arthrofibrosis of commonly affected joints. In addition, we preview several promising modalities under development to ameliorate arthrofibrosis non-surgically and discuss limitations in the field of arthrofibrosis secondary to neuromuscular disorders.

Heterogeneous Distribution of Genetic Mutations in Myosin Binding Protein-C Paralogs

Myosin binding protein-C (MyBP-C) is a sarcomeric protein which regulates the force of contraction in striated muscles. Mutations in the MYBPC family of genes, including slow skeletal (MYBPC1), fast skeletal (MYBPC2) and cardiac (MYBPC3), can result in cardiac and skeletal myopathies. Nonetheless, their evolutionary pattern, pathogenicity and impact on MyBP-C protein structure remain to be elucidated. Therefore, the present study aimed to systematically assess the evolutionarily conserved and epigenetic patterns of MYBPC family mutations. Leveraging a machine learning (ML) approach, the Genome Aggregation Database (gnomAD) provided variants in MYBPC1, MYBPC2, and MYBPC3 genes. This was followed by an analysis with Ensembl’s variant effect predictor (VEP), resulting in the identification of 8,618, 3,871, and 3,071 variants in MYBPC1, MYBPC2, and MYBPC3, respectively. Missense variants comprised 61%–66% of total variants in which the third nucleotide positions in the codons were highly altered. Arginine was the most mutated amino acid, important because most disease-causing mutations in MyBP-C proteins are arginine in origin. Domains C5 and C6 of MyBP-C were found to be hotspots for most mutations in the MyBP-C family of proteins. A high percentage of truncated mutations in cMyBP-C cause cardiomyopathies. Arginine and glutamate were the top hits in fMyBP-C and cMyBP-C, respectively, and tryptophan and tyrosine were the most common among the three paralogs changing to premature stop codons and causing protein truncations at the carboxyl terminus. A heterogeneous epigenetic pattern was identified among the three MYBP-C paralogs. Overall, it was shown that databases using computational approaches can facilitate diagnosis and drug discovery to treat muscle disorders caused by MYBPC mutations.

First report of SYNE1 arthrogryposis multiplex congenita from Saudi Arabia with a novel mutation: a case report

BACKGROUND

Myogenic Arthrogryposis Multiplex Congenita type 3 (AMC-3), is a rare congenital condition characterized by severe hypotonia, club feet, and multiple joint contractures often affecting both arms and legs which start prior to birth.

CASE PRESENTATION

We report a full-term neonate born to first-degree cousins from fourth-generation consanguineous families, who had with antenatal history of reduced fetal movements. At birth, he was noticed to have bilateral club feet, arthrogryposis, severe hypotonia, and absent deep tendon reflexes. The patient developed difficulty in breathing probably attributed to his generalized severe hypotonia, necessitating mechanical ventilation. His creatinine-phospho-kinase, electromyogram, and brain magnetic resonance imaging were normal. Whole-exome sequencing (WES) was requested for the genetic diagnosis of the case. WES identified a novel homozygous variant c.23415-3799C > G p. in the synaptic nuclear envelope protein1 [SYNE1] gene. Seven out of 20 bioinformatic in silico programs predicted a pathogenic effect for this variant. Segregation analysis of the variant in the parents and siblings revealed that both parents and one sibling were heterozygous for the same mutation which proved the variant significance and its autosomal recessive pattern of inheritance.

CONCLUSIONS

AMC3 should be suspected in patients with decreased fetal movements, severe hypotonia, absent deep tendon reflexes, and arthrogryposis. SYNE1 gene mutations can be the underlying genetic defect and molecular genetic testing can prove the diagnosis.

A pathogenic mechanism associated with myopathies and structural birth defects involves TPM2-directed myogenesis

Nemaline myopathy (NM) is the most common congenital myopathy, characterized by extreme weakness of the respiratory, limb, and facial muscles. Pathogenic variants in Tropomyosin 2 (TPM2), which encodes a skeletal muscle-specific actin binding protein essential for sarcomere function, cause a spectrum of musculoskeletal disorders that include NM as well as cap myopathy, congenital fiber type disproportion, and distal arthrogryposis (DA). The in vivo pathomechanisms underlying TPM2-related disorders are unknown, so we expressed a series of dominant, pathogenic TPM2 variants in Drosophila embryos and found 4 variants significantly affected muscle development and muscle function. Transient overexpression of the 4 variants also disrupted the morphogenesis of mouse myotubes in vitro and negatively affected zebrafish muscle development in vivo. We used transient overexpression assays in zebrafish to characterize 2 potentially novel TPM2 variants and 1 recurring variant that we identified in patients with DA (V129A, E139K, A155T, respectively) and found these variants caused musculoskeletal defects similar to those of known pathogenic variants. The consistency of musculoskeletal phenotypes in our assays correlated with the severity of clinical phenotypes observed in our patients with DA, suggesting disrupted myogenesis is a potentially novel pathomechanism of TPM2 disorders and that our myogenic assays can predict the clinical severity of TPM2 variants.

Diagnostic yield of exome sequencing in congenital vertical talus

BACKGROUND

Congenital vertical talus (CVT), also known as "rocker-bottom foot", is a rare foot deformity associated with a dislocation of the talonavicular joint. Although genetic causes of CVT have been described in single isolated and syndromic families, whole-exome sequencing (WES) of large cohorts have not yet been reported.

METHODS

In this study, 62 probands with CVT were evaluated for likely causative single nucleotide variants (SNVs) and copy number variants (CNVs) using WES. Segregation of variants within families was determined by Sanger sequencing.

RESULTS

In this cohort, CVT occurred as an isolated anomaly in 75.8% (47/62) and was familial in 19.3% (12/62) of cases. Analysis of WES data led to the identification of likely causative variants in known disease genes in 30.6% (19/62) of all CVT probands. More than one proband had likely causative SNVs in TSHZ1, GDF5, and LMX1B. Only two probands had likely causative CNVs: a chromosome 12q13.13 deletion of the 5' HOXC gene cluster, and a chromosome 18q22.3q23 deletion involving TSHZ1. Familial CVT was strongly predictive of identifying a molecular diagnosis [75% (9/12) of familial cases compared to 20% (10/50) of non-familial cases (Chi-square test, P-value = 0.0002)]. There was no difference in the solved rate based on isolated or syndromic presentation, unilateral or bilateral affectation, or sex.

CONCLUSIONS

CVT is genetically heterogeneous and more often caused by SNVs than CNVs. There is a high yield of WES in familial CVT cases (∼75%). Additional research is needed to identify the causes of sporadic CVT, which had much lower solved rates.

The Hand in Distal Arthrogryposis

Distal arthrogryposis is the second most common type of arthrogryposis after amyoplasia and is defined as arthrogryposis that affects hands and feet; it is mostly inherited in an autosomal-dominant fashion. This review discusses up-to-date background information, clinical features, and treatment of distal arthrogryposis in hands concentrating on camptodactyly, thumb-in-palm deformity, and windblown hand deformity, which are the most common and functionally limiting deformities. Treating these deformities should be individualized and follow a multidisciplinary approach. Most deformities can be initially treated nonoperatively, and if not responsive, operative treatment may be pursued to improve function. Surgery primarily aims to release soft-tissue contractures, rebalance muscle forces, and may need bony correction based on the deficits of each case. Current literature suggests that early treatment leads to better outcomes. However, reported cases are scarce, and no consensus or gold standard for treatment exists. Therefore, long-term (multicenter) studies are needed to assess outcomes and standardize the treatment of such deformities whenever possible.

Arthrogryposis multiplex congenita: a 28-year retrospective study

AIM

To identify all patients with arthrogryposis multiplex congenita presenting to a specialized pediatric orthopedic institution over a 28-year period; classify them into three groups (general arthrogryposis not otherwise specified [NOS], amyoplasia, or distal arthrogryposis); report the frequency of various musculoskeletal features; and determine the rate of operative treatment.

METHOD

Patients with arthrogryposis under the age of 18 years who presented between 1990 and 2017 were included. Patients were placed into one of three groups based on clinical features and family history when available. Age of presentation, joint involvement, and utilization of surgical treatment were recorded.

RESULTS

There were 417 patients in total (184 females, 233 males); 235 patients (56.4%) had general arthrogryposis NOS, 107 (25.7%) had amyoplasia, and 75 (18.0%) had distal arthrogryposis. Patients with amyoplasia presented at a younger age (median 4mo) than those with general arthrogryposis NOS (median 1y 3mo, p=0.005), and had a lower rate of spine involvement than patients with general arthrogryposis NOS (p=0.004) and distal arthrogryposis (p=0.023). The average number of surgeries across all patients was 1.9 (SD 2.2).

INTERPRETATION

Pediatric patients with amyoplasia present to orthopedic care earlier and are less likely to have spine involvement than other forms of arthrogryposis. Multiple surgeries are common among all patients with arthrogryposis.