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Distal arthrogryposis with impaired proprioception and touch (DAIPT) is an autosomal recessive neurogenetic disorder caused by homozygous pathogenic variants in the PIEZO2 gene. Here we present four Omani families with multiple affected members with DAIPT. The genetic diagnosis was established by whole exome sequencing and we identified a previously unreported homozygous missense variant PIEZO2 : c.1591T > C, P.(Trp531Arg) in one family with two affected members. All patients showed clinical manifestation shortly after birth including transient respiratory insufficiency, significant hypotonia, and gross motor developmental delay with preserved cognitive function. The skeletal manifestation including arthrogryposis is more pronounced with age as we saw in our older patient. This case report will be of importance for physicians and genetic counsellors for faster diagnosis and for offering carrier testing for at-risk family members as part of the premarital testing program, which could help in reducing the burden of this disorder.

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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.

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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.

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Distal arthrogryposis type 5D (DA5D) is clinically characterized by knee extension contractures, distal joint contractures, clubfoot, micrognathia, ptosis, and scoliosis. We report nine affected individuals from eight unrelated Indian families with DA5D. Although the overall musculoskeletal phenotype is not very distinct from other distal arthrogryposis, the presence of fixed knee extension contractures with or without scoliosis could be an important early pointer to DA5D. We also report a possible founder variant in ECEL1 along with four novel variants and further expand the genotypic spectrum of DA5D.

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BACKGROUND: The MYH3-associated myosinopathies comprise a spectrum of rare neuromuscular disorders mainly characterized by distal arthrogryposis with or without other features like pterygia and vertebrae fusion. CPSKF1B (contractures, pterygia, and spondylocarpotarsal fusion syndrome1B) is the only known autosomal recessiveMYH3-associated myosinopathy so far, with no more than two dozen cases being reported. MATERIALS AND METHODS: A boy with CPSKF1B was recruited and subjected to a comprehensive clinical and imaging evaluation. Genetic detection with whole-exome sequencing (WES) was performed on the patient and extended family members to identify the causative variation. A series of in silico and in vitro investigations were carried out to verify the pathogenicity of the two variants of the identified compound heterozygous variation. RESULTS: The patient exhibited moderate CPSKF1B symptoms including multiarticular contractures, webbed neck, and spondylocarpotarsal fusion. WES detected a compound heterozygous MYH3 variation consisting of two variants, namely NM_002470.4: c.3377A>G; p. (E1126G) and NM_002470.4: c.5161-2A>C. It was indicated that the NM_002470.4: c.3377A>G; p. (E1126G) variant mainly impaired the local hydrogen bond formation and impacted the TGF-B pathway, while the NM_002470.4: c.5161-2A>C variant could affect the normal splicing of pre-mRNA, resulting in the appearance of multiple abnormal transcripts. CONCLUSIONS: The findings of this study expanded the mutation spectrum of CPSKF1B, provided an important basis for the counseling of the affected family, and also laid a foundation for the functional study of MYH3 mutations.

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Dominant missense variants in MYBPC1 encoding slow Myosin Binding Protein-C (sMyBP-C) have been increasingly linked to arthrogryposis syndromes and congenital myopathy with tremor. Herein, we describe novel compound heterozygous variants - NM_002465.4:[c.2486_2492del];[c.2663A > G] - present in fibronectin-III (Fn-III) C7 and immunoglobulin (Ig) C8 domains, respectively, manifesting as severe, early-onset distal arthrogryposis type-1, with the carrier requiring intensive care and several surgical interventions at an early age. Computational modeling predicts that the c.2486_2492del p.(Lys829IlefsTer7) variant destabilizes the structure of the Fn-III C7 domain, while the c.2663A > G p.(Asp888Gly) variant causes minimal structural alterations in the Ig C8 domain. Although the parents of the proband are heterozygous carriers for a single variant, they exhibit no musculoskeletal defects, suggesting a complex interplay between the two mutant alleles underlying this disorder. As emerging novel variants in MYBPC1 are shown to be causatively associated with musculoskeletal disease, it becomes clear that MYBPC1 should be included in relevant genetic screenings.

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Mutations at a highly conserved homologous residue in three closely related muscle myosins cause three distinct diseases involving muscle defects: R671C in ß-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 ß, embryonic, and perinatal myosin subfragment-1. We found large effects in the developmental myosins but minimal effects in ß 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 ß 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 ß, 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.

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The mechanosensitive PIEZO channel family has been linked to over 26 disorders and diseases. Although progress has been made in understanding these channels at the structural and functional levels, the underlying mechanisms of PIEZO-associated diseases remain elusive. In this study, we engineered four PIEZO-based disease models using CRISPR/Cas9 gene editing. We performed an unbiased chemical mutagen-based genetic suppressor screen to identify putative suppressors of a conserved gain-of-function variant pezo-1[R2405P] that in human PIEZO2 causes distal arthrogryposis type 5 (DA5; p. R2718P). Electrophysiological analyses indicate that pezo-1(R2405P) is a gain-of-function allele. Using genomic mapping and whole-genome sequencing approaches, we identified a candidate suppressor allele in the C. elegans gene gex-3. This gene is an ortholog of human NCKAP1 (NCK-associated protein 1), a subunit of the Wiskott-Aldrich syndrome protein (WASP)-verprolin homologous protein (WAVE/SCAR) complex, which regulates F-actin polymerization. Depletion of gex-3 by RNAi, or with the suppressor allele gex-3(av259[L353F]), significantly increased brood size and ovulation rate, as well as alleviating the crushed oocyte phenotype of the pezo-1(R2405P) mutant. Expression of GEX-3 in the soma is required to rescue the brood size defects in pezo-1(R2405P) animals. Actin organization and orientation were disrupted and distorted in the pezo-1 mutants. Mutation of gex-3(L353F) partially alleviated these defects. The identification of gex-3 as a suppressor of the pathogenic variant pezo-1(R2405P) suggests that the PIEZO coordinates with the cytoskeleton regulator to maintain the F-actin network and provides insight into the molecular mechanisms of DA5 and other PIEZO-associated diseases.

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Contraction of the human sarcomere is the result of interactions between myosin cross-bridges and actin filaments. Pathogenic variants in genes such as MYH7, TPM1, and TNNI3 that encode parts of the cardiac sarcomere cause muscle diseases that affect the heart, such as dilated cardiomyopathy and hypertrophic cardiomyopathy. In contrast, pathogenic variants in homologous genes such as MYH2, TPM2, and TNNI2 that encode parts of the skeletal muscle sarcomere cause muscle diseases affecting skeletal muscle, such as distal arthrogryposis (DA) syndromes and skeletal myopathies. To date, there have been few reports of genes (e.g., MYH7) encoding sarcomeric proteins in which the same pathogenic variant affects skeletal and cardiac muscle. Moreover, none of the known genes underlying DA have been found to contain pathogenic variants that also cause cardiac abnormalities. We report five families with DA because of heterozygous missense variants in the gene actin, alpha, cardiac muscle 1 (ACTC1). ACTC1 encodes a highly conserved actin that binds to myosin in cardiac and skeletal muscle. Pathogenic variants in ACTC1 have been found previously to underlie atrial septal defect, dilated cardiomyopathy, hypertrophic cardiomyopathy, and left ventricular noncompaction. Our discovery delineates a new DA condition because of variants in ACTC1 and suggests that some functions of ACTC1 are shared in cardiac and skeletal muscle.

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Key Clinical Message: Congenital Contractures of Limbs and Face, Hypotonia, and Developmental Delay (CLIFAHDD) syndrome is a recently described type of distal arthrogryposis which unlike other subtypes is associated with developmental delay and various neurologic presentation. Epilepsy and ataxia have been reported. We add paroxysmal dyskinesia to the clinical spectrum. Understanding the molecular mechanism can help developing targeted therapy in future. Abstract: This study resulted in identification of a novel variant in NALCN gene leading to autosomal dominant CLIFAHDD syndrome. Our patient presented with a form of nonepileptic paroxysmal dyskinesia. This is a new phenotype that has not been described previously.

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Arthrogryposis multiplex congenita (AMC) is defined as "a group of congenital conditions characterized by joint contractures in two or more body areas." Given its heterogeneity, the definition of AMC has changed multiple times. This scoping review provides an overview of how AMC is defined in scientific publications, on existing knowledge and trends regarding the concept of AMC. Our review illuminates possible knowledge gaps and provides directions for future research. A scoping review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines. Quantitative studies on AMC from 1995 to date were included. We summarized information about definitions/descriptions of AMC, study objectives, study designs, methods, funding, and involvement of patient organizations. A total of 2729 references were screened, and 141 articles fulfilled our inclusion criteria. Our scoping revealed that the majority of publications were cross-sectional or retrospective studies of children and young people, commonly about orthopedic management. Explicit or good definitions of AMC were provided in 86% of the cases. Recent publications on AMC mostly used consensus-based definitions. The research gaps were primarily related to adults, aging, etiology, and new medical treatment, in addition to implications on daily life.

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Distal arthrogryposis is a rare disease caused by mutations in genes encoding proteins involved in muscle fiber contraction. Its joint contracture mainly involves distal joint contracture, and scoliosis is often accompanied by pelvic tilt and abnormal lordosis.This article reviewed the clinical characteristics of a patient with distal arthrogryposis combined with scoliosis. The patient was a 14-year-old male. His back was found that uneven 6 years ago for no obvious reason, and his scoliosis was gradually worsened. The patient had flexion contractures of both hands and bilateral knees since childhood, and no special treatment was given. There was no obvious restriction in the movement of the spine, the thoracic segment was convex on the right side, and the lumbar segment was convex on the left side. The genetic diagnosis was MYL11 gene mutation, which was consistent with the clinical manifestations of distal arthrogryposis combined with scoliosis. Posterior scoliosis correction and growing rod placement were performed electively. The operation went smoothly and the trunk balance was satisfactory. The clinical characteristics of this disease are summarized to improve our understanding of the disease.

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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.

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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.

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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.

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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.

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Arthrogryposis is a heterogenous condition with a wide variety of etiological causes. It has been subdivided clinically based on the presence of additional features. Dominant gain of function (GoF) pathogenic variants in PIEZO2 have been associated with several forms of arthrogryposis. Previous reports have focused on diagnosis and clinical features. We report a three-generation family with four affected individuals with a known pathogenic GoF change p.(Glu2727del) in PIEZO2. All family members presented at birth with distal arthrogryposis and ophthalmoplegia but have varied in their subsequent clinical course with differences in mobility and joint restriction. In the longer term, other features have presented including dysphagia, back pain and spinal stenosis-like symptoms, raised intraocular pressure, and progressive restrictive lung disease. As far as we know, this is the first report detailing the longitudinal follow-up of a three-generation family which highlights potential long-term complications in patients with PIEZO2-related arthrogryposis. We present this family to demonstrate the importance of long-term follow-up for the clinical management of this group of patients.

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RESUMEN Introducción: El síndrome de Freeman-Sheldon es un síndrome hereditario raro, de severidad variable que afecta principalmente la cara, manos y pies, sin preferencia de género, étnica o geográfica. Objetivo: Caracterizar clínicamente a un paciente con síndrome Freeman-Sheldon. Presentación del caso: Niña ecuatoriana de 6 años de edad, hija de madre de 43 años y padre de 42 años, la cuarta de 6 hermanos, todos sanos, no historia de consanguinidad. La cual presenta cara parecida a una máscara, ojos hundidos, puente nasal ancho, boca pequeña con apariencia de silbador, hoyuelo cutáneo en mentón en forma de H, defecto en las manos, contractura de los dedos con desviación cubital y pies equinovaro, dificultad para la marcha y baja talla. Conclusiones: El síndrome de Freeman-Sheldon es un síndrome raro que afecta principalmente la cara y las extremidades de los pacientes, cuyo diagnóstico clínico es posible luego de un examen físico exhaustivo.

ABSTRACT Introduction: Freeman-Sheldon syndrome is a rare hereditary syndrome of varying severity that mainly affects the face, hands and feet, without gender, ethnic or geographical preference. Objective: Clinically characterize a patient with Freeman-Sheldon syndrome. Presentation of the case: Ecuadorian girl, 6 years old, daughter of mother of 43 years and father of 42 years, the fourth of 6 brothers, all healthy, not history of consanguinity. She presents mask-like face, sunken eyes, wide nasal bridge, small mouth with the appearance of a whistler, skin dimple on the chin in the shape of an H, defect in the hands, contracture of the fingers with ulnar deviation and clubfoot, also walking difficulty and short height. Conclusions: Freeman-Sheldon syndrome is a rare syndrome that mainly affects the face and limbs of patients, whose clinical diagnosis is possible after a thorough physical examination.

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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.

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