Fetal Akinesia Research Articles

Genetic diagnosis and clinical evaluation of severe fetal akinesia syndrome.

ObjectiveIn this retrospective study, we describe the clinical course, ultrasound findings and genetic investigations of fetuses affected by fetal akinesia.Materials and MethodsWe enrolled 22 eukaryotic fetuses of 18 families, diagnosed with fetal akinesia between 2008 and 2016 at the Department of Obstetrics and Feto‐Maternal Medicine at the Medical University of Vienna. Routine genetic evaluation included karyotyping and chromosomal microarray analysis. Retrospectively, exome sequencing was performed in the index case of 11 families, if stored DNA was available. Confirmation analyses and genetic diagnosis of siblings were performed by using Sanger sequencing.ResultsWhole exome sequencing identified pathogenic variants of CNTN1, RYR1, NEB, GLDN, HRAS and TNNT3 in six cases of 11 families. In three of these families, the variants were confirmed in the respective sibling.ConclusionsThe present study demonstrates a high diagnostic yield of exome sequencing in fetuses affected by akinesia syndrome, especially if family history is positive. Still, in a large part the underlying genetic cause remained unknown, whereas precise clinical evaluation in combination with exome sequencing shows to be the best tool to find the disease causing variants.

New Compound Heterozygous Splice Site Mutations of the Skeletal Muscle Ryanodine Receptor (RYR1) Gene Manifest Fetal Akinesia: A Linkage with Congenital Myopathies

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene have been linked to malignant hyperthermia susceptibility, central core disease, and minicore myopathy with external ophthalmoplegia. RYR1 is an intracellular calcium release channel and plays a crucial role in the sarcoplasmic reticulum and transverse tubule connection. Here, we report 2 fetuses from the same parents with compound heterozygous mutations in the RYR1 gene (c.10347+1G>A and c.10456-2Α>G) who presented with fetal akinesia and polyhydramnios at 27 and 19 weeks of gestation with intrauterine growth restriction in the third pregnancy. The prospective parents of the fetuses were heterozygous carriers for c.10456-2Α>G (mother) and c.10347+1G>A (father). Both mutations affect splice sites resulting in dysfunctional protein forms probably missing crucial domains of the C-terminus. Our findings reveal a new RYR1 splice site mutation (c.10456-2Α>G) that may be associated with the clinical features of myopathies, expanding the RYR1 spectrum related to these pathologies.

The genomic and clinical landscape of fetal akinesia

PurposeFetal akinesia has multiple clinical subtypes with over 160 gene associations, but the genetic etiology is not yet completely understood. MethodsIn this study, 51 patients from 47 unrelated families were analyzed using next-generation sequencing (NGS) techniques aiming to decipher the genomic landscape of fetal akinesia (FA). ResultsWe have identified likely pathogenic gene variants in 37 cases and report 41 novel variants. Additionally, we report putative pathogenic variants in eight cases including nine novel variants. Our work identified 14 novel disease–gene associations for fetal akinesia: ADSSL1, ASAH1, ASPM, ATP2B3,EARS2, FBLN1, PRG4, PRICKLE1, ROR2, SETBP1, SCN5A, SCN8A, and ZEB2. Furthermore, a sibling pair harbored a homozygous copy-number variant inTNNT1, an ultrarare congenital myopathy gene that has been linked to arthrogryposis via Gene Ontology analysis. ConclusionOur analysis indicates that genetic defects leading to primary skeletal muscle diseases might have been underdiagnosed, especially pathogenic variants in RYR1. We discuss three novel putative fetal akinesia genes: GCN1,IQSEC3 and RYR3. Of those, IQSEC3, andRYR3 had been proposed as neuromuscular disease–associated genes recently, and our findings endorse them as FA candidate genes. By combining NGS with deep clinical phenotyping, we achieved a 73% success rate of solved cases.

Single-channel properties of skeletal muscle ryanodine receptor pore Δ4923FF4924 in two brothers with a lethal form of fetal akinesia

Ryanodine receptor ion channels (RyR1s) release Ca2+ ions from the sarcoplasmic reticulum to regulate skeletal muscle contraction. By whole-exome sequencing, we identified the heterozygous RYR1 variant c.14767_14772del resulting in the in-frame deletion p.(Phe4923_Phe4924del) in two brothers with a lethal form of the fetal akinesia deformation syndrome (FADS). The two deleted phenylalanines (RyR1-Δ4923FF4924) are located in the S6 pore-lining helix of RyR1. Clinical features in one of the two siblings included severe hypotonia, thin ribs, swallowing inability, and respiratory insufficiency that caused early death. Functional consequences of the RyR1-Δ4923FF4924 variant were determined using recombinant 2,200-kDa homotetrameric and heterotetrameric RyR1 channel complexes that were expressed in HEK293 cells and characterized by cellular, electrophysiological, and computational methods. Cellular Ca2+ release in response to caffeine indicated that the homotetrameric variant formed caffeine-sensitive Ca2+ conducting channels in HEK293 cells. In contrast, the homotetrameric channel complex was not activated by Ca2+ and did not conduct Ca2+ based on single-channel measurements. The computational analysis suggested decreased protein stability and loss of salt bridge interactions between RyR1-R4944 and RyR1-D4938, increasing the electrostatic interaction energy of Ca2+ in a region 20 Å from the mutant site. Co-expression of wild-type and mutant RyR1s resulted in Ca2+-dependent channel activities that displayed intermediate Ca2+ conductances and suggested maintenance of a reduced Ca2+ release in the two patients. Our findings reveal that the RYR1 pore variant p.(Phe4923_Phe4924del) attenuates the flow of Ca2+ through heterotetrameric channels, but alone was not sufficient to cause FADS, indicating additional genetic factors to be involved.

Schaaf-Yang Syndrome: An Example of Genomic Imprinting and Expanding Phenotype

Schaf-Yang Syndrome is a rare genetic condition, produced by a mutation in the MAGEL2 gene, located at the level of chromosome 15, in the Prader-Willi Syndrome region, with which it shares some physical similarity. The phenotype is variable and ranges from fetal akinesia to an important neurobehavioral phenotype and contractures of the small finger joints that are very characteristic. The gene has a maternal imprint and the phenotype will only be expressed when the mutated allele has been transmitted parentally. We present the case of a 2-and-a-half-year-old male from Ecuador, whose most prominent signs were in the beginning a marked macroglossia that gave a certain rough facial appearance, as well as bilateral camptodactyly of the 3rd and 4th fingers. The history of a previous sister who died at age 8 with a diagnosis of hypothyroidism, and clinical similarity to this new baby, led the clinical orientation to the screening of a potentially autosomal recessive condition. The genetic tests performed as part of the differential diagnosis where to pathologies such as Becwith-Wiedeman Syndrome, Mucopolysaccharidosis and Congenital Hypothyroidism. The clinical elements of this case are compared with those described in the literature with this rare genetic syndrome, and the clinical evolution of dysmorphic patterns in young children is emphasized in order to achieve a better diagnostic certainty. We emphasize the features of macroglossia as a probably expanding phenotype in this rare condition. The presentation of this clinical case shows that the factors that alter the segregation of simple mutations such as the case of the genetic imprint, found in this patient, constitute an event that hinders the interpretation of inheritance patterns and should always be taken into account in genetic counseling.

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.

Diagnosis of fetal non-chromosomal abnormalities on routine ultrasound examination at 11-13 weeks' gestation.

To examine the performance of the routine 11-13-week scan in detecting fetal non-chromosomal abnormalities. This was a retrospective study of prospectively collected data from 100 997 singleton pregnancies attending for a routine ultrasound examination of fetal anatomy, performed according to a standardized protocol, at 11-13 weeks' gestation. All continuing pregnancies had an additional scan at 18-24 weeks and 71 754 had a scan at either 30-34 or 35-37 weeks. The final diagnosis of fetal abnormality was based on the results of postnatal examination in cases of live birth and on the findings of the last ultrasound examination in cases of pregnancy termination, miscarriage or stillbirth. The performance of the 11-13-week scan in the detection of fetal abnormalities was determined. The study population contained 1720 (1.7%) pregnancies with a fetal abnormality, including 474 (27.6%) detected on the first-trimester scan, 926 (53.8%) detected on the second-trimester scan and 320 (18.6%) detected in the third trimester or postnatally. At 11-13 weeks' gestation, we diagnosed all cases of acrania, alobar holoprosencephaly, encephalocele, tricuspid or pulmonary atresia, pentalogy of Cantrell, ectopia cordis, exomphalos, gastroschisis and body-stalk anomaly and > 50% of cases of open spina bifida, hypoplastic left heart syndrome, atrioventricular septal defect, complex heart defect, left atrial isomerism (interrupted inferior vena cava with normal intracardiac anatomy), lower urinary tract obstruction, absence of extremities, fetal akinesia deformation sequence and lethal skeletal dysplasia. Common abnormalities that were detected in < 10% of cases at 11-13 weeks included ventriculomegaly, agenesis of the corpus callosum, isolated cleft lip, congenital pulmonary airway malformation, ventricular septal defect, abdominal cysts, unilateral renal agenesis or multicystic kidney, hydronephrosis, duplex kidney, hypospadias and talipes. A routine 11-13-week scan, carried out according to a standardized protocol, can identify many severe non-chromosomal fetal abnormalities. A summary statistic of the performance of the first-trimester scan is futile because some abnormalities are always detectable, whereas others are either non-detectable or sometimes detectable. To maximize prenatal detection of abnormalities, additional scans in both the second and third trimesters are necessary. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

I.6Arthrogryposis multiplex congenita; new genes & old acquaintances

Arthrogryposis multiplex congenita (AMC) is a multi-facetted disease that is characterized by congenital contractures in two or more body regions, which might or might not be accompanied by additional symptoms, being termed "syndromic" or "isolated" arthrogryposis. The disease is further clinically divided into "proximal" and "distal" arthrogryposis, depending on whether large or smaller distal joints of hands and feet are predominantly affected. AMC results from an overall lack of fetal movement (fetal akinesia), which in turn might have a multitude of etiologies with presently more than 120 having a genetic underpinning. Genetic defects mainly revolve around the development and maintenance of the motor unit and the reflex arch. Mutations may affect proteins with a role in the development of connective and contractile muscle tissue, in the biogenesis of the neuromuscular endplate, and in neuronal myelination. Other proteins may be involved in neuronal pathfinding, signaling, and cellular transport mechanisms or participate in the local or central control of muscle tension. This lecture will give an overview over the multiple etiologies and will try a classification on genetic and clinical grounds, which could support the diagnosing physicians to find the correct diagnosis in their patients. Finally, we will present a novel genetic defect that causes spontaneously regressing AMC associated with dilated cardiomyopathy.

P.235Clinico-pathological characterisation of CACNA1S related congenital myopathy in children

Mutations in the CACNA1S gene were recently identified as a new cause of congenital myopathy (CM). To date only a few cases have been described, with limited phenotypic data. We report the clinical, pathological and radiological phenotype in five children with genetically confirmed CACNA1S-CM. →Patients were referred to our national highly specialised service for CM at The Dubowitz Neuromuscular Centre, UK. We conducted retrospective case note analysis. Two patients had recessive inheritance and three autosomal dominant. →Four of five patients (age range 7-18 years) had severe neonatal presentation with foetal akinesia, weakness, hypotonia, contractures, feeding difficulties and respiratory compromise. The 5th patient presented with motor delay in infancy. All five patients had proximal predominant, bulbar and facial weakness but showed spontaneous improvement over time. Ophthalmoplegia was noted in three. Two patients remain non-ambulant. Two developed scoliosis. Two are on nocturnal non-invasive ventilation initiated at age of 5 months and 7 years. All apart from one required nasogastric/gastrostomy feeding up until 2-5 years of age, but all were able to feed orally from age 5 years. One patient had clear history of periodic weakness well responding to Acetazolamide. Two children reported fatigue and limited endurance but no abnormalities of neuromuscular transmission were detected. All muscle biopsies showed fibre size variation and marked slow fibre predominance. Additional findings included mild central nucleation, few central cores and focally accentuated pseudo-dystrophic changes. Three out of the five patients had abnormal lower limb muscle MRI but with no specific muscle pattern. →CACNA1S related myopathy is a recently described form of congenital myopathy and should be considered in cases of undiagnosed dominant and recessive congenital myopathies with phenotypical features presented above.

O.16Diagnosis of fetal akinesia and arthrogryposis by panel sequencing and functional genomics

O.16Diagnosis of fetal akinesia and arthrogryposis by panel sequencing and functional genomics

Listeriosis During Pregnancy and in Newborns: 18 Years of Data From a Large Tertiary Hospital in Singapore.

A 20-year retrospective review at a tertiary hospital in Singapore identified 11 cases of perinatal listeriosis in maternal-fetal pairs (incidence, 4.8 cases per 100 000 live births). Fever, meconium-stained amniotic fluid, and fetal akinesia during the third trimester were associated with listeriosis. In this study early directed antibiotic therapy resulted in favorable outcomes.

Fetal arthrogryposis multiplex congenita/fetal akinesia deformation sequence (FADS)-Aetiology, diagnosis, and management.

Arthrogryposis multiplex congenita (AMC) refers to an aetiologically heterogenous condition, which consists of joint contractures affecting two or more joints starting prenatally. The incidence is approximately one in 3000 live births; however, the prenatal incidence is higher, indicating a high intrauterine mortality. Over 320 genes have been implicated showing the genetic heterogeneity of the condition. AMC can be of extrinsic aetiology resulting from intrauterine crowding secondary to congenital structural uterine abnormalities (eg, bicornuate or septate uterus), uterine tumors (eg, fibroid), or multifetal pregnancy or intrinsic/primary/fetal aetiology, due to functional abnormalities in the brain, spinal cord, peripheral nerves, neuromuscular junction, muscles, bones, restrictive dermopathies, tendons and joints. Unlike many of the intrinsic/primary/fetal causes which are difficult to treat, secondary AMC can be treated by physiotherapy with good response. Primary cases may present prenatally with fetal akinesia associated with joint contractures and occasionally brain abnormalities, decreased muscle bulk, polyhydramnios, and nonvertex presentation while the secondary cases usually present with isolated contractures. Complete prenatal and postnatal investigations are needed to identify an underlying aetiology and provide information regarding its prognosis and inheritance, which is critical for the obstetrical care providers and families to optimize the pregnancy management and address future reproductive plans.

Severe biallelic loss-of-function mutations in nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2) in two fetuses with fetal akinesia deformation sequence

The three nicotinamide mononucleotide adenylyltransferase (NMNAT) family members synthesize the electron carrier nicotinamide adenine dinucleotide (NAD+) and are essential for cellular metabolism. In mammalian axons, NMNAT activity appears to be required for axon survival and is predominantly provided by NMNAT2. NMNAT2 has recently been shown to also function as a chaperone to aid in the refolding of misfolded proteins. Nmnat2 deficiency in mice, or in its ortholog dNmnat in Drosophila, results in axon outgrowth and survival defects. Peripheral nerve axons in NMNAT2-deficient mice fail to extend and innervate targets, and skeletal muscle is severely underdeveloped. In addition, removing NMNAT2 from established axons initiates axon death by Wallerian degeneration. We report here on two stillborn siblings with fetal akinesia deformation sequence (FADS), severely reduced skeletal muscle mass and hydrops fetalis. Clinical exome sequencing identified compound heterozygous NMNAT2 variant alleles in both cases. Both protein variants are incapable of supporting axon survival in mouse primary neuron cultures when overexpressed. In vitro assays demonstrate altered protein stability and/or defects in NAD+ synthesis and chaperone functions. Thus, both patient NMNAT2 alleles are null or severely hypo-morphic. These data indicate a previously unknown role for NMNAT2 in human neurological development and provide the first direct molecular evidence to support the involvement of Wallerian degeneration in a human axonal disorder. SignificanceNicotinamide Mononucleotide Adenylyltransferase 2 (NMNAT2) both synthesizes the electron carrier Nicotinamide Adenine Dinucleotide (NAD+) and acts a protein chaperone. NMNAT2 has emerged as a major neuron survival factor. Overexpression of NMNAT2 protects neurons from Wallerian degeneration after injury and declining levels of NMNAT2 have been implicated in neurodegeneration. While the role of NMNAT2 in neurodegeneration has been extensively studied, the role of NMNAT2 in human development remains unclear. In this work, we present the first human variants in NMNAT2 identified in two fetuses with severe skeletal muscle hypoplasia and fetal akinesia. Functional studies in vitro showed that the mutations impair both NMNAT2 NAD+ synthase and chaperone functions. This work identifies the critical role of NMNAT2 in human development.

Molecular autopsy by trio exome sequencing (ES) and postmortem examination in fetuses and neonates with prenatally identified structural anomalies

PurposeTo determine the diagnostic yield of combined exome sequencing (ES) and autopsy in fetuses/neonates with prenatally identified structural anomalies resulting in termination of pregnancy, intrauterine, neonatal, or early infant death. MethodsES was undertaken in 27 proband/parent trios following full autopsy. Candidate pathogenic variants were classified by a multidisciplinary clinical review panel using American College of Medical Genetics and Genomics (ACMG) guidelines. ResultsA genetic diagnosis was established in ten cases (37%). Pathogenic/likely pathogenic variants were identified in nine different genes including four de novo autosomal dominant, three homozygous autosomal recessive, two compound heterozygous autosomal recessive, and one X-linked. KMT2D variants (associated with Kabuki syndrome postnatally) occurred in two cases. Pathogenic variants were identified in 5/13 (38%) cases with multisystem anomalies, in 2/4 (50%) cases with fetal akinesia deformation sequence, and in 1/4 (25%) cases each with cardiac and brain anomalies and hydrops fetalis. No pathogenic variants were detected in fetuses with genitourinary (1), skeletal (1), or abdominal (1) abnormalities. ConclusionThis cohort demonstrates the clinical utility of molecular autopsy with ES to identify an underlying genetic cause in structurally abnormal fetuses/neonates. These molecular findings provided parents with an explanation of the developmental abnormality, delineated the recurrence risks, and assisted the management of subsequent pregnancies.

Electrodiagnostic elucidation of a novel variant in the acetylcholine receptor gene identified by rapid trio exome sequencing, leading to the diagnosis and treatment of congenital myasthenia syndrome in an infant presenting with fetal akinesia deformation sequence. (P3.7-006)

Electrodiagnostic elucidation of a novel variant in the acetylcholine receptor gene identified by rapid trio exome sequencing, leading to the diagnosis and treatment of congenital myasthenia syndrome in an infant presenting with fetal akinesia deformation sequence. (P3.7-006)

Fetal akinesia deformation sequence, arthrogryposis multiplex congenita, and bilateral clubfeet: Is motor assessment of additional value for in utero diagnosis? A 10-year cohort study.

ObjectiveThe diagnosis of fetal akinesia deformation sequence (FADS) is a challenge. Motor assessment is of additional value to advanced ultrasound examinations (AUE) for in utero FADS diagnosis before 24 weeks of gestation.MethodsAll consecutive fetuses with greater than or equal to two contractures on the 20 week structural anomaly scan (2007–2016) were included. Findings at AUE, including motor assessment were analysed and related to outcome.ResultsSixty‐six fetuses fulfilled the inclusion criteria. On the basis of the first AUE, FADS was suspected in 13 of 66, arthrogryposis multiplex congenita (AMC) in 12 of 66, bilateral pes equinovares (BPEV) in 40 of 66, and Holt‐Oram syndrome in one of 66. On the basis of the first motor assessment, the suspected diagnosis changed in 19 of 66, in 13 of 66 worsening to FADS, six of 66 amelioration from FADS, and confirmed FADS in seven of 13. The result was 20 FADS, seven AMC, and 38 BPEV. Second AUE in 44 fetuses showed additional contractures in two of eight FADS, and one intrauterine fetal death (IUFD). The second motor assessment changed the diagnosis in three of 43, one worsening from BPEV into FADS, two ameliorations from FADS, and confirmed FADS in seven by deterioration of motility. The result was nine FADS, six AMC, and 29 BPEV.ConclusionThe results suggest that motor assessment has additional value to distinguish between FADS, AMC, and BPEV.

Homozygous/compound heterozygote RYR1 gene variants: Expanding the clinical spectrum.

The ryanodine receptor 1 (RYR1) is a calcium release channel essential for excitation-contraction coupling in the sarcoplasmic reticulum of skeletal muscles. Dominant variants in the RYR1 have been well associated with the known pharmacogenetic ryanodinopathy and malignant hyperthermia. With the era of next-generation gene sequencing and growing number of causative variants, the spectrum of ryanodinopathies has been evolving with dominant and recessive variants presenting with RYR1-related congenital myopathies such as central core disease, minicore myopathy with external ophthalmoplegia, core-rod myopathy, and congenital neuromuscular disease. Lately, the spectrum was broadened to include fetal manifestations, causing a rare recessive and lethal form of fetal akinesia deformation sequence syndrome (FADS)/arthrogryposis multiplex congenita (AMC) and lethal multiple pterygium syndrome. Here we broaden the spectrum of clinical manifestations associated with homozygous/compound heterozygous RYR1 gene variants to include a wide range of manifestations from FADS through neonatal hypotonia to a 35-year-old male with AMC and PhD degree. We report five unrelated families in which three presented with FADS. One of these families was consanguineous and had three affected fetuses with FADS, one patient with neonatal hypotonia who is alive, and one individual with AMC who is 35 years old with normal intellectual development and uses a wheelchair. Muscle biopsies on these cases demonstrated a variety of histopathological abnormalities, which did not assist with the diagnostic process. Neither the affected living individuals nor the parents who are obligate heterozygotes had history of malignant hyperthermia.

Type (0) spinal muscular atrophy associated with fractures at birth

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of alpha motor neurons in the spinal cord, resulting in progressive proximal muscle weakness and paralysis. In addition to the three classical SMA types mentioned worldwide, a new form known as Type 0 with intrauterine onset in the form of fetal akinesia and profound hypotonia manifesting as birth asphyxia and a progressive, and early fatal course has been described. Here, we report a case of Type 0 SMA presenting with bilateral symmetrical fracture of long bones at birth, which has been reported miniscule in the world literature.

Rare etiology of arthrogryposis multiplex congenita at term: congenital cytomegalovirus infection

Abstract Background Arthrogryposis multiplex congenita is the presence of multiple congenital contractures of two or more body parts. Congenital cytomegalovirus (CMV) infection is a rare etiology of arthrogryposis. Case presentation We report a case of intrauterine fetal akinesia and arthrogryposis multiplex congenita delivered at term with subsequent neonatal demise. Placental pathology and autopsy revealed congenital CMV infection. Conclusions Evaluation for potential CMV infection is an important part of the arthrogryposis evaluation which is often missed due to lack of maternal infectious symptoms during pregnancy.

Fetal Neuropathology and Abnormal Motor Assessment—Fetal Akinesia Deformation Sequence: KANET is of Additional Value for the In Utero Diagnosis

Fetal Neuropathology and Abnormal Motor Assessment—Fetal Akinesia Deformation Sequence: KANET is of Additional Value for the In Utero Diagnosis