Biallelic truncating TTN variants in M-band encoding exons cause a fetal lethal titinopathy.

To report two novel TTN variants associated with fetal recessive titinopathy, thereby broadening the range of TTN variants that can lead to titinopathy. Clinical information on the fetus and parents was gathered, and genomic DNAs were extracted from the fetal tissue and family members' peripheral blood samples. Exome sequencing on fetal DNA was performed and following bioinformatics analysis, the suspected pathogenic variants were confirmed through Sanger sequencing. Prenatal ultrasound performed at 29 weeks of gestation revealed hydrops fetalis, decreased fetal movements, multiple joint contractures and polyhydramnios. Intrauterine fetal death was noted in the third trimester. Exome sequencing revealed compound heterozygous variants in the TTN gene: a paternally inherited allele c.101227C>T (p.Arg33743Ter) and a maternally inherited c.104254C>T (p.Gln34752Ter) allele. These variants have not been previously reported and are evaluated to be likely pathogenic according to the American College of Medical Genetics and Genomics guidelines. We report a fetus with hydrops fetalis and arthrogryposis multiplex congenita associated with a compound heterozygote in the TTN gene. Our report broadens the clinical and genetic spectrum associated with the TTN-related conditions.

Foetal Akinesia Deformation Sequence: A Rare Lethal Entity.

Foetal akinesia deformation sequence (FADS) represents a group of disorders resulting from absent or diminished in utero foetal mobility. The aetiology is multifactorial, including genetic, environmental, maternal, and foetal causes. The absence of foetal movements leading to multiple joint contractures, pulmonary hypoplasia, and intrauterine growth restriction are the key features of foetal akinesia deformation sequence. Herein we describe the case of a 30-year-old gravida 4 (para 2+1) who came for foetal ultrasound at 28 weeks of gestation due to decreased foetal movements. Ultrasound showed features of FADS with fixed flexed position of foetal limbs, pulmonary hypoplasia, polyhydramnios, and intrauterine growth restriction. The timely use of ultrasound enables early detection of these cases and aids in appropriate counselling and management.

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.

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.

Prenatal diagnosis of SMPD4 loss - A neurodevelopmental disorder with microcephaly, arthrogryposis and structural brain anomalies.

SMPD4 loss is a rare neurodevelopmental disorder that leads to severe mental and physical disability and early death in infancy. Most cases of this genetic condition have been diagnosed postnatally. This article focuses on the prenatal findings of affected fetuses. The phenotypes can include growth restriction, arthrogryposis (clenched hands, foot deformity), as well as cerebral abnormalities (simplified gyral pattern/lissencephaly, cerebellar hypoplasia, corpus callosum deformity). SMPD4 loss is detectable via exome sequencing. Here, two fetuses displayed a homozygotic pathogen variant in the SMPD4 gene, encoding for the enzyme Sphingomyelinase-4. Both parents were heterozygous carriers of the pathogenic variant. On detection of the above mentioned signs exome sequencing is indicated, with focus on the SMPD4 gene.

Recognizable Pattern of Arthrogryposis and Congenital Myopathy Caused by the Recurrent TTN Metatranscript-only c.39974-11T > G Splice Variant.

INTRODUCTION: Arthrogryposis is characterized by the presence of multiple contractures at birth and can be caused by pathogenic variants in TTN (Titin). Exons and variants that are not expressed in one of the three major isoforms of titin are referred to as "metatranscript-only" and have been considered to be only expressed during fetal development. Recently, the metatranscript-only variant (c.39974-11T > G) in TTN with a second truncating TTN variant has been linked to arthrogryposis multiplex congenita and myopathy. METHODS: Via exome sequencing we identified the TTN c.39974-11T > G splice variant in trans with one of three truncating variants (p.Arg8922*, p.Lys32998Asnfs*63, p.Tyr10345*) in five individuals from three families. Clinical presentation and muscle ultrasound as well as MRI images were analyzed. RESULTS: All five patients presented with generalized muscular hypotonia, reduced muscle bulk, and congenital contractures most prominently affecting the upper limbs and distal joints. Muscular hypotonia persisted and contractures improved over time. One individual, the recipient twin in the setting of twin-to-twin transfusion syndrome, died from severe cardiac hypertrophy 1 day after birth. Ultrasound and MRI imaging studies revealed a recognizable pattern of muscle involvement with striking fibrofatty involvement of the hamstrings and calves, and relative sparing of the femoral adductors and anterior segment of the thighs. CONCLUSION: The recurrent TTN c.39974-11T > G variant consistently causes congenital arthrogryposis and persisting myopathy providing evidence that the metatranscript-only 213 to 217 exons impact muscle elasticity during early development and beyond. There is a recognizable pattern of muscle involvement, which is distinct from other myopathies and provides valuable clues for diagnostic work-up.

Improvement of Pulmonary Function in Arthrogryposis Multiplex Congenita Patients Undergoing Posterior Spinal Fusion Surgery for Concomitant Scoliosis: A Minimum of 3-Year Follow-up.

OBJECTIVE: We sought to investigate the long-term outcome of pulmonary function for arthrogryposis multiplex congenita (AMC) patients undergoing posterior spinal fusion (PSF) and to further determine influential factors. METHODS: Eighteen AMC patients with a minimum of 3-year follow-up after PSF were prospectively collected. All the patients underwent a pulmonary function test before surgery and at the final follow-up. The percentage predicted values of vital capacity (VC%) and forced vital capacity (FVC%) were recorded. The following radiographic parameters were collected including Cobb angle and thoracic kyphosis. The total lung volumes (TLV) were measured on the image of 3-dimensional computed tomography scan by the reconstruction software. RESULTS: There were 10 males and 8 females with a mean age of 13.8 ± 6.1 years. The mean preoperative VC% and FVC% were 40.5% ± 7.6% and 39.5% ± 4.7%, which were significantly increased to 52.0% ± 7.5% and 51.2% ± 6.8% at the final follow-up (P < 0.001). Besides, there was remarkable improvement in terms of TLV (1.57 ± 0.2 L vs. 2.39 ± 0.6 L, P < 0.001). Remarkable correlations were observed between TLV and pulmonary function tests (r = 0.79, P < 0.001 for VC%; r = 0.78, P < 0.001 for FVC%). Multiple regression analysis showed that 2 variables including Δ thoracic kyphosis and Δ Cobb angle were independently associated with the improvement of pulmonary function. CONCLUSIONS: The pulmonary function of AMC patients can be well improved through PSF surgery. It was remarkably associated with the correction of curve magnitude and restoration of thoracic kyphosis.

Care Pathway for Foetal Joint Contractures, Foetal Akinesia Deformation Sequence, and Arthrogryposis Multiplex Congenita.

INTRODUCTION: The majority of arthrogryposis multiplex congenita (AMC) and lethal forms of AMC such as foetal akinesia deformation sequence (FADS) cases are missed prenatally. We have demonstrated the additional value of foetal motor assessment and evaluation in a multidisciplinary team for the period 2007-2016. An applied care pathway was developed for foetuses presenting with joint contracture(s) in one anatomic region (e.g., talipes equinovarus [TEV]), more than one body part with non-progressive contractures and motility (AMC) and with deterioration over time (FADS). METHODS: The multidisciplinary team of Amsterdam University Medical Centre Expertise Centre FADS and AMC developed the care pathway. Additional tools are provided including a motor assessment by ultrasound examination and a post-mortem assessment form. RESULTS: An eight-step care pathway is presented with a proposed timing for prenatal sonographic examination, genetic examinations, multidisciplinary meetings, prenatal and postnatal counselling of the parents by a specialist also treating after birth, and the follow-up of prenatal and postnatal findings with counselling for future pregnancies. DISCUSSION/CONCLUSION: The scheduled serial structural and motor sonograpahic assessment together with follow-up examinations and genetic analysis should be tailored per prenatal centre per available resources. The multidisciplinary care pathway may pave the way to increase the detection rate and diagnosis of isolated contracture(s), TEV with underlying genetic causes, and the rare phenotypes AMC/FADS and prompt treatment after birth within expertise teams.

Postnatal Diagnostic Workup in Children With Arthrogryposis: A Series of 82 Patients.

OBJECTIVE: To describe a postnatal series of patients with arthrogryposis multiplex congenita by the causal mechanisms involved. METHODS: In this single-center study, the local data warehouse was used to identify patients with arthrogryposis multiplex congenita. Patients were classified into different etiologic groups. RESULTS: Of 82 patients included, the most frequent cause of arthrogryposis multiplex congenita was a neuromuscular disorder (39%), including skeletal muscle (n = 19), neuromuscular junction (n = 3), and peripheral nerve (n = 11) involvement. In other subgroups, 19 patients (23%) were classified by disorders in the central nervous system, 5 (6%) in connective tissue, 7 (8.5%) had mixed mechanisms, and 18 (22%) could not be classified. Contractures topography was not associated with a causal mechanism. Cerebral magnetic resonance imaging (MRI), electroneuromyography, and muscle biopsy were the most conclusive investigations. Metabolic investigations were normal in all the patients tested. Targeted or whole exome sequencing diagnostic rates were 51% and 71%, respectively. Thirty-three percent of patients died (early death occurred in patients with polyhydramnios, prematurity, and ventilatory dependency). DISCUSSION: The benefits of a precise diagnosis in the neonatal period include more tailored management of arthrogryposis multiplex congenita and better genetic information.

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

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

Fetal early motor neuron disruption and prenatal molecular diagnosis in a severe BICD2-opathy.

BICD2 (BICD Cargo Adaptor 2, MIM*609797) mutations are associated with severe prenatal-onset forms of spinal muscular atrophy, lower extremity-predominant 2B (SMALED2B MIM 618291) or milder forms with childhood-onset (SMALED2A MIM 615290). Etiopathogenesis is not fully clarified and a wide spectrum of phenotypic presentations is reported, ranging from extreme prenatal forms with adverse outcome, to slow progressive late-onset forms. We report a fetus at 22 gestational weeks with evidence of Arthrogryposis Multiplex Congenita on ultrasound, presenting with fixed extended lower limbs and flexed upper limbs, bilateral clubfoot and absent fetal movements. A trio-based prenatal Exome Sequencing was performed, disclosing a de novo heterozygous pathogenic in frame deletion (NM_015250.3: c.1636_1638delAAT; p.Asn546del) in BICD2. After pregnancy termination, quantitative analysis on NeuN immunostained spinal cord sections of the ventral horns, revealed that neuronal density was markedly reduced compared to the one of an age-matched normal fetus and an age-matched type-I Spinal Muscular Atrophy sample, used as a comparative model. The present case, the first prenatally diagnosed and neuropathologically characterized, showed an early motor neuron loss in SMALED2B, providing further insight into the pathological basis of BICD2-opathies.

Prognostic significance of prenatal ultrasound in fetal arthrogryposis multiplex congenita.

PURPOSE: Fetal arthrogryposis multiplex congenita (AMC) describes a heterogeneous disease entity characterized by multiple contractures affecting at least two different body areas. The aim of our study was to identify additional sonographic abnormalities in fetuses with AMC Type I-III associated with an unfavorable prognosis and to describe when those signs were first detected. METHODS: This retrospective study included 41 pregnancies of suspected AMC diagnosed 1999-2017 at our tertiary referral center. The affected pregnancies were divided into the 3 AMC subgroups; the time of detection and outcome were analyzed. Prenatal sonograms, pediatric charts, genetic tests, and autopsy reports were studied. RESULTS: Pregnancy outcome data were verifiable in 34 out of 41 cases; in 27 cases, AMC was confirmed. Hydrops was present in 50% of postnatally deceased fetuses, 53% of cases resulting in termination of pregnancy vs. 0% of the surviving 8 children. Absent stomach filling was found in 67% of the children with neonatal death. After subcategorization, the limb-involvement-only-group, 8% showed hydrops vs. 100% in system anomaly group vs. 70% in neuromuscular dysfunction cohort (p = 0.001). Scoliosis, nuchal edema, and absent stomach filling were significantly indicating for a neurological etiology. CONCLUSION: In addition to disease-defining sonographic findings, those with prognostic significance were identified. Hydrops, nuchal edema, scoliosis and absent stomach filling were associated with unfavorable outcomes implicating a neuromuscular etiology. This knowledge can help to predict the further course of the disease and support patient counseling.

The Electrophysiologic and Ultrasonographic Change after Carpal Tunnel Release in a Patient with Hereditary Neuropathy with Liability to Pressure Palsy.

Hereditary neuropathy with liability to pressure palsy (HNPP) often manifests via peripheral nerve entrapment including median nerve compression at the carpal tunnel. However, there are few reports on surgical interventions for focal compression of the median nerve at the wrist in patients with HNPP. We report a case of a patient with HNPP who improved clinically, electrophysiologically, and ultrasonographically after carpal tunnel release (CTR). A 56-year-old woman presented with an 18-month history of pain in both thumbs. Nerve conduction study (NCS) revealed bilateral median neuropathy at the wrist. Ultrasonography demonstrated a markedly increased cross-sectional area (CSA) of both median nerves. Gene analysis revealed a deletion of the PMP22 gene. She received bilateral CTR. Follow-up NCS at one year demonstrated the improvement of motor and sensory conduction; follow-up ultrasonography revealed significantly reduced CSA. Our case suggests that surgical decompression can be applicable to well-selected patients with HNPP.

Bone densities and bone geometry in children and adolescents with arthrogryposis.

OBJECTIVE: To describe bone densitometry results using lumbar spine dual-energy X-ray absorptiometry and forearm peripheral quantitative computed tomography (pQCT) in children with arthrogryposis multiplex congenita (AMC). STUDY DESIGN: Prospective study. RESULTS: Lumbar spine areal bone mineral density (BMD) was measured in 58 participants (mean age 6.8 years, range 1 month to 19.7 years; 26 males). The diagnostic subgroup was Amyoplasia in 27 participants, distal arthrogryposis (unclassified, n = 13; type 2A, n = 1; type 2B, n = 2; type 8, n = 2) in 18 patients, an unclassified form of arthrogryposis in 6 patients, and a syndromic form of arthrogryposis in 7 patients. The mean lumbar spine areal BMD was -0.4 (SD: 1.5) which was significantly below 0 (p < 0.05, one-sample t-test). The mean lumbar spine bone mineral apparent density z-score (+0.4 [SD: 1.4]), a measure that is largely independent of bone size, was not significantly different from 0 (P > 0.05). A subset of 22 patients aged 6 years or older (mean age 10.9 years, 11 males) had forearm pQCT analysis. Mean z-scores for trabecular and cortical volumetric BMD at the radius were similar to healthy controls. Radius periosteal bone circumference and bone mineral content were appropriate for height. These densitometric results did not differ between patients with Amyoplasia or individuals with other diagnoses. CONCLUSIONS: Low areal BMD in children and adolescents with AMC reflects their smaller bone size rather than a specific bone mass deficit. These data do not suggest that children and adolescents with AMC in general require regular monitoring by bone densitometry unless there are specific clinical concerns.

Early open reduction of dislocated hips using a modified Smith-Petersen approach in arthrogyposis multiplex congenita.

BACKGROUND: Arthrogryposis multiplex congenita (AMC) is a rare syndrome with multiple joint contractures. Within the medical community, there is controversy surrounding AMC in terms of the ideal surgical approach and age for performing a reduction of dislocated hips. The purpose of this retrospective study was to evaluate the clinical outcomes of early open reduction of infant hip dislocation with arthrogryposis multiplex congenita following a modified Smith-Petersen approach that preserves the rectus femoris. METHODS: From 2010 to 2017, we performed this procedure on 28 dislocated hips in 20 infants under 12 months of age with AMC. The clinical and radiology data were reviewed retrospectively. The mean age at surgery was 6.9 ± 5.1 months, with a mean follow-up of 42.4 ± 41.1 months. RESULTS: After open reduction, the average hip acetabular index (AI), the international hip dysplasia institute classification (IHDI), and the hip range of motion significantly improved (all P < 0.001). After the surgery, 16 patients were community walkers, and four patients were home walkers. Three hips in two patients required secondary revision surgery for residual acetabular dysplasia with combined pelvic osteotomy and femoral osteotomy. Seven of the hips that had been operated on showed signs of avascular necrosis (AVN). Among them, four were degree II, two were degree III, and one was degree IV. Multiple linear regression analysis demonstrated that greater age (in months) heightened the risk for secondary revision surgery (P = 0.032). CONCLUSIONS: The modified Smith-Petersen approach preserving the rectus femoris is an encouraging and safe option for treating hip dislocation in young AMC patients (before 12 months). If surgery takes place at less than 12 months of age for patients with AMC, this earlier open reduction for hip dislocation may reduce the chances of secondary revision surgery. LEVEL OF EVIDENCE: IV, retrospective non-randomized study.

Recessive mutations in SCYL2 cause a novel syndromic form of arthrogryposis in humans.

Arthrogryposis multiplex congenita (AMC) is an important birth defect with a significant genetic contribution. Many syndromic forms of AMC have been described, but remain unsolved at the molecular level. In this report, we describe a novel syndromic form of AMC in two multiplex consanguineous families from Saudi Arabia and Oman. The phenotype is highly consistent, and comprises neurogenic arthrogryposis, microcephaly, brain malformation (absent corpus callosum), optic atrophy, limb fractures, profound global developmental delay, and early lethality. Whole-exome sequencing revealed a different homozygous truncating variant in SCYL2 in each of the two families. SCYL2 is a component of clathrin-coated vesicles, and deficiency of its mouse ortholog results in a severe neurological phenotype that largely recapitulates the phenotype observed in our patients. Our results suggest that severe neurogenic arthrogryposis with brain malformation is the human phenotypic consequence of SCYL2 loss of function mutations.

Length-dependent MRI of hereditary neuropathy with liability to pressure palsies.

OBJECTIVE: Hereditary neuropathy with liability to pressure palsies (HNPP) is caused by heterozygous deletion of the peripheral myelin protein 22 (PMP22) gene. Patients with HNPP present multifocal, reversible sensory/motor deficits due to increased susceptibility to mechanical pressure. Additionally, age-dependent axonal degeneration is reported. We hypothesize that length-dependent axonal loss can be revealed by MRI, irrespective of the multifocal phenotype in HNPP. METHODS: Nerve and muscle MRI data were acquired in the proximal and distal leg of patients with HNPP (n = 10) and matched controls (n = 7). More specifically, nerve magnetization transfer ratios (MTR) were evaluated to assay proximal-to-distal gradients in nerve degeneration, while intramuscular fat percentages (Fper ) were evaluated to assay muscle fat replacement following denervation. Neurological disabilities were assessed via the Charcot-Marie-Tooth neuropathy score (CMTNS) for correlation with MRI. RESULTS: Fper values were elevated in HNPP proximal muscle (9.8 ± 2.2%, P = 0.01) compared to controls (6.9 ± 1.0%). We observed this same elevation of HNPP distal muscles (10.5 ± 2.5%, P < 0.01) relative to controls (6.3 ± 1.1%). Additionally, the amplitude of the proximal-to-distal gradient in Fper was more significant in HNPP patients than controls (P < 0.01), suggesting length-dependent axonal loss. In contrast, nerve MTR values were similar between HNPP subjects (sciatic/tibial nerves = 39.4 ± 2.0/34.2 ± 2.5%) and controls (sciatic/tibial nerves = 37.6 ± 3.8/35.5 ± 1.2%). Proximal muscle Fper values were related to CMTNS (r = 0.69, P = 0.03), while distal muscle Fper and sciatic/tibial nerve MTR values were not related to disability. INTERPRETATION: Despite the multifocal nature of the HNPP phenotype, muscle Fper measurements relate to disability and exhibit a proximal-to-distal gradient consistent with length-dependent axonal loss, suggesting that Fper may be a viable biomarker of disease progression in HNPP.

Null variants in AGRN cause lethal fetal akinesia deformation sequence.

We present a case of lethal fetal akinesia deformation sequence (FADS) caused by a frameshift variant in trans with a 148 kbp deletion encompassing 3-36 exons of AGRN. Pathogenic variants in AGRN have been described in families with a form of congenital myasthenic syndrome (CMS), manifesting in the early childhood with variable fatigable muscle weakness. To the best of our knowledge, this is the first case of FADS caused by defects in AGRN gene. FADS has been reported to be caused by pathogenic variants in genes previously associated with CMS including these involved in endplate development and maintenance: MuSK, DOK7, and RAPSN. FADS seems to be the most severe form of CMS. None of the reported in the literature CMS cases associated with AGRN had two null variants, like the case presented herein. This indicates a strong genotype-phenotype correlation.