Asymptomatic maternal myasthenia as a cause of the Pena-Shokeir phenotype

Maternal immunoglobulin treatment can reduce severity of fetal acetylcholine receptor antibody-associated disorders (FARAD)

BACKGROUND

Fetal acetylcholine receptor antibody-associated disorders (FARAD), caused by in utero exposure to maternal antibodies directed against the fetal acetylcholine receptor (AChR), is a rare condition occurring in newborns of myasthenic mothers. Only two cases of FARAD children born to asymptomatic mothers are published.

CASE

We report a completely asymptomatic mother of two FARAD children presenting exclusively with positive AChR antibodies. After birth, the first child needed intensive care therapy due to generalized hypotonia, respiratory problems, dysphagia, necessitating tube feeding and gastrostomy. FARAD was suspected because of ptosis, a hypomimic face, and confirmed by increased AChR antibodies in the mother. The mother became pregnant again 2 years later. Since FARAD is likely to reoccur and it is known that intensity of maternal myasthenia gravis treatment determines postnatal outcome, monthly intravenous immunoglobulin (IVIG) therapy was started at 12 weeks gestational age. The second child needed a short mask ventilation for initial stabilization at birth, but her muscle weakness improved rapidly and tube feeding was not necessary. Similar to her sister a tent-shaped mouth and a somewhat myopathic face persisted, but motor milestones were reached in time.

CONCLUSIONS

These observations highlight that FARAD is an important differential diagnosis of genetically determined congenital neuromuscular disorders even in asymptomatic mothers, and that IVIG therapy during the pregnancy has the potential to improve the outcome of the children.

The emerging spectrum of fetal acetylcholine receptor antibody-related disorders (FARAD)

In utero exposure to maternal antibodies targeting the fetal acetylcholine receptor isoform (fAChR) can impair fetal movement, leading to arthrogryposis multiplex congenita (AMC). Fetal AChR antibodies have also been implicated in apparently rare, milder myopathic presentations termed fetal acetylcholine receptor inactivation syndrome (FARIS). The full spectrum associated with fAChR antibodies is still poorly understood. Moreover, since some mothers have no myasthenic symptoms, the condition is likely underreported, resulting in failure to implement effective preventive strategies. Here we report clinical and immunological data from a multicentre cohort (n = 46 cases) associated with maternal fAChR antibodies, including 29 novel and 17 previously reported with novel follow-up data. Remarkably, in 50% of mothers there was no previously established myasthenia gravis (MG) diagnosis. All mothers (n = 30) had AChR antibodies and, when tested, binding to fAChR was often much greater than that to the adult AChR isoform. Offspring death occurred in 11/46 (23.9%) cases, mainly antenatally due to termination of pregnancy prompted by severe AMC (7/46, 15.2%), or during early infancy, mainly from respiratory failure (4/46, 8.7%). Weakness, contractures, bulbar and respiratory involvement were prominent early in life, but improved gradually over time. Facial (25/34; 73.5%) and variable peripheral weakness (14/32; 43.8%), velopharyngeal insufficiency (18/24; 75%) and feeding difficulties (16/36; 44.4%) were the most common sequelae in long-term survivors. Other unexpected features included hearing loss (12/32; 37.5%), diaphragmatic paresis (5/35; 14.3%), CNS involvement (7/40; 17.5%) and pyloric stenosis (3/37; 8.1%). Oral salbutamol used empirically in 16/37 (43.2%) offspring resulted in symptom improvement in 13/16 (81.3%). Combining our series with all previously published cases, we identified 21/85 mothers treated with variable combinations of immunotherapies (corticosteroids/intravenous immunoglobulin/plasmapheresis) during pregnancy either for maternal MG symptom control (12/21 cases) or for fetal protection (9/21 cases). Compared to untreated pregnancies (64/85), maternal treatment resulted in a significant reduction in offspring deaths (P < 0.05) and other complications, with treatment approaches involving intravenous immunoglobulin/ plasmapheresis administered early in pregnancy most effective. We conclude that presentations due to in utero exposure to maternal (fetal) AChR antibodies are more common than currently recognized and may mimic a wide range of neuromuscular disorders. Considering the wide clinical spectrum and likely diversity of underlying mechanisms, we propose 'fetal acetylcholine receptor antibody-related disorders' (FARAD) as the most accurate term for these presentations. FARAD is vitally important to recognize, to institute appropriate management strategies for affected offspring and to improve outcomes in future pregnancies. Oral salbutamol is a symptomatic treatment option in survivors.

Impaired gating of γ- and ε-AChR respectively causes Escobar syndrome and fast-channel myasthenia

OBJECTIVE

To dissect the kinetic defects of acetylcholine receptor (AChR) γ subunit variant in an incomplete form of the Escobar syndrome without pterygium and compare it with those of a variant of corresponding residue in the AChR ε subunit in a congenital myasthenic syndrome (CMS).

METHODS

Whole exome sequencing, α-bungarotoxin binding assay, single channel patch-clamp recordings, and maximum likelihood analysis of channel kinetics.

RESULTS

We identified compound heterozygous variants in AChR γ and ε subunits in three Escobar syndrome (1-3) and three CMS patients (4-6), respectively. Each Escobar syndrome patient carries γP121R along with γV221Afs*44 in patients 1 and 2, and γY63* in patient 3. Three CMS patients share εP121T along with εR20W, εG-8R, and εY15H in patients 4, 5, and 6, respectively. Surface expressions of γP121R- and εP121T-AChR were 80% and 138% of the corresponding wild-type AChR, whereas εR20W, εG-8R, and εY15H reduced receptor expression to 27%, 35%, and 30% of wild-type εAChR, respectively. γV221Afs*44 and γY63* are null variants. Thus, γP121R and εP121T determine the phenotype. γP121R and εP121T shorten channel opening burst duration to 28% and 18% of corresponding wild-type AChR by reducing the channel gating equilibrium constant 44- and 63-fold, respectively.

INTERPRETATION

Similar impairment of channel gating efficiency of a corresponding P121 residue in the acetylcholine-binding site of the AChR γ and ε subunits causes Escobar syndrome without pterygium and fast-channel CMS, respectively, suggesting that therapy for the fast-channel CMS will benefit Escobar syndrome.

Fetal akinesia deformation sequence with pontocerebellar hypoplasia, and migration and gyration defects

Fetal akinesia deformation sequence (FADS), or Pena-Shokeir phenotype is a constellation of deformational changes resulting from decreased or absent fetal movement, and include arthrogryposis, and craniofacial and central nervous system anomalies. We report an autopsy case of a 36-6/7week female neonate with a normal female karyotype and chromosome microarray demonstrating findings consistent with FADS. We provide a detailed examination of the severe and complex central nervous system abnormalities, including marked pontocerebellar hypoplasia and cortical and cerebellar migration and gyration defects. This case represents a rare detailed examination of the central nervous system of a patient with FADS.

Ultrasonographic evidence of persistent hyperextension of the fetal neck: is it a true sign? A diagnostic and prognostic challenge

OBJECTIVE

The purpose of this study was to evaluate the clinical evolution, structural anomalies associated and neonatal outcomes of fetal neck hyperextension in two cases with prenatal ultrasound diagnosis in two different gestational ages.

METHODS

In 2019, two cases of fetal hyperextension came to our attention. Follow-up information was obtained from hospital medical records and obstetrical care providers.

RESULTS

Two woman were investigated in our institution for the presence of fetal abnormalities in the II and III trimester, respectively. In both cases, fetal attitude presented persistent fetal neck hyperextension. One of the two fetuses had a mild ventriculomegaly and suspected for micrognathia. Both had an amniotic fluid increase. One of two had no movement in the lower and upper limbs in ultrasound scans associated with club foot and suspected scoliosis. Both were born by cesarean section with pretty different prognosis: one healthy baby had a retarded psychomotor development and the other one died after 6 months. A precise diagnosis was possible only in one case.

CONCLUSION

The early identification of a fetus with persistent hyperextension of the fetal head should require a detailed ultrasound exam for structural abnormalities and a careful prenatal counseling due to possible postnatal outcome.

Italian recommendations for diagnosis and management of congenital myasthenic syndromes

Congenital myasthenic syndromes (CMS) are genetic disorders due to mutations in genes encoding proteins involved in the neuromuscular junction structure and function. CMS usually present in young children, but perinatal and adult onset has been reported. Clinical presentation is highly heterogeneous, ranging from mild symptoms to severe manifestations, sometimes with life-threatening respiratory episodes, especially in the first decade of life. Although considered rare, CMS are probably underestimated due to diagnostic difficulties. Because of the several therapeutic opportunities, CMS should be always considered in the differential diagnosis of neuromuscular disorders. The Italian Network on CMS proposes here recommendations for proper CMS diagnosis and management, aiming to guide clinicians in their practical approach to CMS patients.

Pena-Shokeir syndrome: current management strategies and palliative care

Pena-Shokeir syndrome (PSS) type 1, also known as fetal akinesia deformation sequence, is a rare genetic syndrome that almost always results in intrauterine or early neonatal death. It is characterized by markedly decreased fetal movements, intrauterine growth restriction, joint contractures, short umbilical cord, and features of pulmonary hypoplasia. Antenatal diagnosis can be difficult. Ultrasound features are varied and may overlap with those of Trisomy 18. The poor prognosis of PSS is due to pulmonary hypoplasia, which is an important feature that distinguishes PSS from arthrogryposis multiplex congenital without pulmonary hypoplasia, which has a better prognosis. If diagnosed in the antenatal period, a late termination of pregnancy can be considered following ethical discussion (if the law allows). In most cases, a diagnosis is only made in the neonatal period. Parents of a baby affected with PSS require detailed counseling that includes information on the imprecise recurrence risks and a plan for subsequent pregnancies.

Clinical follow-up of pregnancy in myasthenia gravis patients

This study aimed to analyze the outcome and impact of pregnancy in women with myasthenia gravis (MG). Obstetric and clinical data were retrospectively analyzed before, during and after pregnancy. Predictors of outcome were studied. We included 35 pregnancies from 21 MG patients. In the course of MG symptoms in 30 pregnancies with live births, 50% deteriorated (mainly during the second trimester, p = 0.028), 30% improved, and 20% remained unchanged. The deterioration group had more frequent abnormal repetitive nerve stimulation (RNS) (p = 0.028) and lower myasthenia gravis composite (MGC) scores (p = 0.045) before pregnancy. The improvement group was associated with higher MGC scores (p = 0.012) before pregnancy. The no-change group was associated with longer duration of MG (p = 0.026) and normal RNS (p = 0.008) before pregnancy. The course of MG in the second pregnancy was different from that in the previous pregnancy in 65.3% of cases. Obstetric complications were reported in 20 pregnancies; the most common was preterm premature rupture of membranes (PPROM) (25.8%), and the most severe were abortion (11.4%) and fetal death (2.9%). Most of the patients delivered via caesarean section (66.7%). Spinal anesthesia was performed in 73.3%. Transient neonatal myasthenia gravis occurred in 12.9% of live-born infants, and no predictors were found. In conclusion, severity and duration of MG, RNS and treatment influence MG and pregnancy. Pregnant MG patients have greater rates of PPROM and caesarean delivery. Our data suggest that duration of MG, MGC and RNS before pregnancy may be useful in helping to predict the course of MG during pregnancy.

Current Role of Fetal Magnetic Resonance Imaging in Body Anomalies

Fetal MR body applications have become more common in recent years as both in utero therapies, including fetoscopic surgery, and improvements in perinatal care have increased the demand for precise antenatal anatomic detail. This article discusses the variety of fast imaging sequences available to the fetal imager and describes their applications to both common and unusual congenital pathologies, including of the neck, chest, abdomen/pelvis and musculoskeletal systems.

Maternal antibodies from mothers of children with autism alter brain growth and social behavior development in the rhesus monkey

Antibodies directed against fetal brain proteins of 37 and 73 kDa molecular weight are found in approximately 12% of mothers who have children with autism spectrum disorder (ASD), but not in mothers of typically developing children. This finding has raised the possibility that these immunoglobulin G (IgG) class antibodies cross the placenta during pregnancy and impact brain development, leading to one form of ASD. We evaluated the pathogenic potential of these antibodies by using a nonhuman primate model. IgG was isolated from mothers of children with ASD (IgG-ASD) and of typically developing children (IgG-CON). The purified IgG was administered to two groups of female rhesus monkeys (IgG-ASD; n=8 and IgG-CON; n=8) during the first and second trimesters of pregnancy. Another control group of pregnant monkeys (n=8) was untreated. Brain and behavioral development of the offspring were assessed for 2 years. Behavioral differences were first detected when the macaque mothers responded to their IgG-ASD offspring with heightened protectiveness during early development. As they matured, IgG-ASD offspring consistently deviated from species-typical social norms by more frequently approaching familiar peers. The increased approach was not reciprocated and did not lead to sustained social interactions. Even more striking, IgG-ASD offspring displayed inappropriate approach behavior to unfamiliar peers, clearly deviating from normal macaque social behavior. Longitudinal magnetic resonance imaging analyses revealed that male IgG-ASD offspring had enlarged brain volume compared with controls. White matter volume increases appeared to be driving the brain differences in the IgG-ASD offspring and these differences were most pronounced in the frontal lobes.

Fetal acetylcholine receptor inactivation syndrome and maternal myasthenia gravis: a case report

Fetal acetylcholine receptor inactivation syndrome is a rare condition occurring in newborns of myasthenic mothers, characterized by bulbar and facial weakness after recovery from the generalized muscle weakness. Antibodies against fetal subunit of acetylcholine receptor seem to have a pathogenetic role leading to long-lasting injury in vulnerable muscle groups. We report a girl, born to a myasthenic mother, who presented with this peculiar phenotype associated with high titers of antibodies specific to the fetal acetylcholine receptor. Although the infant had partial clinical improvement she died prematurely of aspiration pneumonia. We believe that this is a rare but possibly unrecognized condition that should be considered in newborns with persistent myasthenic features even in asymptomatic mothers, and clinicians should consider supportive intervention to avoid fatal complications.

Acquired myasthenia gravis in childhood

PURPOSE OF REVIEW

This review discusses recent studies on myasthenia gravis with onset in childhood (juvenile myasthenia gravis) and neonatal myasthenia gravis.

RECENT FINDINGS

The occurrence of myasthenia gravis in childhood is strongly influenced by genetic and environmental factors. Juvenile myasthenia gravis is associated with antibodies to the acetylcholine receptor (AChR) in most patients. Thymoma is rare, but often malignant in children. The frequency of juvenile myasthenia gravis with antibodies to the muscle-specific kinase (MuSK) varies markedly in different countries; some distinct features have been described. Management of juvenile myasthenia gravis does not differ, on the whole, from that of adult myasthenia gravis. Timing of thymectomy in young children is still controversial. Maternal antifetal type AChR antibodies can cause persistent focal weakness in the offspring, while neonatal myasthenia gravis associated with MuSK antibodies is often a severe and protracted albeit transient disease.

SUMMARY

Juvenile myasthenia gravis, like its adult-onset counterpart, is a heterogeneous disease. Clinical presentation is influenced by antibody status, ethnicity and age of onset. Treatment is very effective, but guidelines and controlled trials are needed.The risk for neonatal myasthenia gravis appears to be markedly influenced by maternal antibody subclass and antigen specificity. Adequate treatment in mothers can reduce both frequency and severity of neonatal disease.

Diagnostic use of autoantibodies in myasthenia gravis

The diagnostic use of antibodies is dependent on sensitivity and specificity of the methods of antibody detection, which have been developed and improved over the years. Here, we review the different methods for the detection of acetylcholine receptor and muscle-specific kinase antibodies, which are, so far, the only antibodies recognised as pathogenic in myasthenia gravis (MG). Seronegative MG patients will benefit from more sensitive methods of antibody detection. The most recent developments in antibody detection assays, particularly those based on cells expressing target antigens, allow rapid and reliable identification of autoantibodies, improving the diagnosis and treatment of MG patients. The same approaches to antibody detection are now being applied to a wide range of other autoantigens and other autoimmune diseases.

Pena-Shokeir syndrome type I – combination of polyhydramnios and pulmonary hypoplasia in fetal akinesia

A szerzők egy 18 éves, másodszor szülő esetét ismertetik, akinek első terhessége polyhydramnionnal szövődött, majd a 30. gesztációs héten a magzat méhen belüli elhalása következett be. A dysmorph küllemű magzatot akkor lepényleválás miatt császármetszéssel emelték ki, a rendellenességről pontos leírás nem született. Jelen cikkünk tárgyát képező második terhessége 19. hetétől észleltük a később extrém mértéket elérő polyhydramniont, majd a terhesség előrehaladtával sorra jelentkeztek magzati malformatióra utaló ultrahangjelek: abnormális helyzetű végtagok, szűk mellkas, koponya körüli oedema, a gyomortelődés hiánya. A 34. héten tehermentesítő amniocentesis vált szükségessé, az ekkor elvégzett magzati kromoszómavizsgálat normális karyotypust igazolt. A 39. gesztációs héten pozitív amnioszkópos lelet miatti szülésindukció során tartós magzati bradycardia jelentkezett, ezért sürgős császármetszést végeztünk. A 3000 grammos fiú újszülött a komplex resuscitatio ellenére, befolyásolhatatlan légzési elégtelenség miatt 2,5 órás korában exitált. A kórbonctani és hisztopatológiai vizsgálat a következő fenotípusos jegyeket írta le: nagy, oedemás fej, micrognathia, macroglossia, gégeoedema, szűk mellkas tüdőhypoplasiával, gracilis végtagok atrófiás izomzattal, gracilis ujjak karomállásban, valamint rövid köldökzsinór. Az anamnézis, a kórlefolyás és a fenotípusos jegyek alapján felállítható volt az I-es típusú Pena–Shokeir-szindróma diagnózisa. A közlemény második részében irodalmi adatok alapján áttekintjük a kórkép etiológiáját, patogenezisét, praenatalis diagnosztikáját és differenciáldiagnosztikáját, valamint a genetikai tanácsadás szempontjait. Tudomásunk szerint a jelen közleménnyel hazánkban először számolunk be diagnosztizált Pena–Shokeir-szindrómás esetről.

Serial postural and motor assessment of Fetal Akinesia Deformation Sequence (FADS)

BACKGROUND

Fetal Akinesia Deformation Sequence (FADS) is a rare, in most cases autosomal recessive, disorder. Its heterogeneous origin results in variable onset and expression of motor and postural anomalies. DNA-diagnostic possibilities are limited, thus prenatal diagnosis is chiefly dependent on sonographic examinations.

AIM

To explore postural and motor development from a systematic sonographic protocol for fetuses at high risk for FADS. Specific questions are: which motor (i.e., specific movement patterns, quality and quantity of general movements) and postural aspects are most informative about emerging FADS and is the gestational age of onset range of FADS more limited for siblings?

METHODS

Ten families underwent 45, 15-minute sonographic assessments for motility and posture for ten index fetuses with FADS and nine subsequent pregnancies from five families.

RESULTS

FADS was diagnosed between 18 and 33 weeks gestation in ten index pregnancies and between 11 and 18 weeks gestation in 4/9 subsequent pregnancies, 1-12 weeks earlier than their index pregnancies. From the four assessment aspects, posture and movement quality were always abnormal, movement quantity in 7/14 and differentiation into specific movement patterns were reduced in comparison with healthy siblings (p<0.01). Deterioration occurred in a 2 week period.

CONCLUSIONS

Serial postural and qualitative assessments were most informative diagnosing FADS. Quantity and differentiation into specific movement patterns contributed substantially. Onset range of FADS within siblings was suggested to be more limited than between families.

Pena-Shokeir phenotype (fetal akinesia deformation sequence) revisited

BACKGROUND

Pena and Shokeir described the phenotype of two sisters in 1974, and subsequently their features have become recognized as a sequence of deformational changes related to decreased or absent fetal movement (fetal akinesia deformation sequence [FADS]), because of the work of Moessinger (1983).

METHODS

Identification of reported cases by searching Online Mendelian Inheritance in Man, Medlines, the London Dysmorphology Database, and the references found in these articles. These case reports were reviewed, tabulated, and summarized.

RESULTS

It is now possible to recognize at least 20 familial types of Pena-Shokeir phenotype (PSP), based on the differences found in the reports of the natural history and pathology found at fetal and newborn autopsy. In addition, characteristic changes in the central nervous system seen with embryonic/fetal vascular compromise have been recognized in many reported cases. Most of the reported cases of PSP/FADS related to vascular compromise are sporadic, but familial cases have also been reported.

CONCLUSION

Lack of fetal movement (fetal akinesia) in humans produces a recognizable sequence of deformations. Many developmental processes must be accomplished for fetal movement to be normal, and for extra-uterine life to be sustainable. Prenatal diagnosis is possible through real-time ultrasound studies as early as 12 weeks. Most reported cases die in utero, at birth, or in the newborn period. Advances in embryo/fetus pathology have led to the recognition of the many familial subtypes, allowing improved genetic counseling and early recognition in subsequent pregnancies.

Immunity and acquired alterations in cognition and emotion: lessons from SLE

Classic immunologic teaching describes the brain as an immunologically privileged site. Studies of neuroimmunology have focused for many years almost exclusively on multiple sclerosis, a disease in which inflammatory cells actually infiltrate brain tissue, and the rodent model of this disease, experimental allergic encephalitis. Over the past decade, however, increasingly, brain-reactive antibodies have been demonstrated in the serum of patients with numerous neurological diseases. The contribution these antibodies make to neuronal dysfunction has, in general, not been determined. Here, we describe recent studies showing that serum antibodies to the N-methyl-D-aspartate receptor occur frequently in patients with systemic lupus erythematosus and can cause alterations in cognition and behavior following a breach in the blood-brain barrier.

Stereotypies and hyperactivity in rhesus monkeys exposed to IgG from mothers of children with autism

Autism together with Asperger syndrome and pervasive developmental disorder not otherwise specified form a spectrum of conditions (autism spectrum disorders or ASD) that is characterized by disturbances in social behavior, impaired communication and the presence of stereotyped behaviors or circumscribed interests. Recent estimates indicate a prevalence of ASD of 1 per 150 (Kuehn, 2007). The cause(s) of most cases of ASD are unknown but there is an emerging consensus that ASD have multiple etiologies. One proposed cause of ASD is exposure of the fetal brain to maternal autoantibodies during pregnancy [Dalton, P., Deacon, R., Blamire, A., Pike, M., McKinlay, I., Stein, J., Styles, P., Vincent, A., 2003. Maternal neuronal antibodies associated with autism and a language disorder. Ann. Neurol. 53, 533-537]. To provide evidence for this hypothesis, four rhesus monkeys were exposed prenatally to human IgG collected from mothers of multiple children diagnosed with ASD. Four control rhesus monkeys were exposed to human IgG collected from mothers of multiple typically developing children. Five additional monkeys were untreated controls. Monkeys were observed in a variety of behavioral paradigms involving unique social situations. Behaviors were scored by trained observers and overall activity was monitored with actimeters. Rhesus monkeys gestationally exposed to IgG class antibodies from mothers of children with ASD consistently demonstrated increased whole-body stereotypies across multiple testing paradigms. These monkeys were also hyperactive compared to controls. Treatment with IgG purified from mothers of typically developing children did not induce stereotypical or hyperactive behaviors. These findings support the potential for an autoimmune etiology in a subgroup of patients with neurodevelopmental disorders. This research raises the prospect of prenatal evaluation for neurodevelopmental risk factors and the potential for preventative therapeutics.

Severe neonatal myasthenia due to maternal anti-MuSK antibodies

Anti-MuSK antibodies have been reported in about 40-50% of patients with seronegative myasthenia gravis. Curiously, this condition has never been reported in association with fetal or transient neonatal myasthenia gravis, despite a known female predominance. We report the case of a 22-year-old woman who developed seronegative, mild steroid-responsive myasthenia gravis. When aged 26, she gave birth to a baby boy with neonatal myasthenia gravis characterized by hypotonia, stridor and sucking difficulties. Intubation was required for a few weeks. Anti-MuSK antibodies were assessed and found positive in both patients. Progressive hydramnios during the last trimester, with a decrease in spontaneous fetal mobility in the last weeks, long-lasting stridor, ptosis and occasional difficulties in swallowing liquids till two years of age, despite anti-MuSK antibodies becoming negative, suggest a fetal onset. The possible pathophysiology of this disorder, based on recent findings on the expression and function of MuSK protein, is reviewed.

Myasthenia gravis in pregnancy and birth: identifying risk factors, optimising care

Women with myasthenia gravis (MG) have increased risk of pregnancy complications and an adverse pregnancy outcome. This study examined risk factors for such complications in order to improve the care for pregnant MG women. Through the Medical Birth Registry of Norway, 73 MG mothers with 135 births were identified. Their obstetrical and clinical records were examined. Data on pregnancy, delivery and the newborn were combined with information on mother's disease. The risk for neonatal MG was halved if the mother was thymectomized (P = 0.03). Children with neonatal MG were more likely to display signs of foetal distress during delivery (P = 0.05). Only in one-third of the pregnancies did the patient see a neurologist during pregnancy. These patients used MG medication more often during pregnancy (P = 0.001), and were more likely to be thymectomized (P = 0.007). They also had a higher rate of elective sections (P = 0.009). Thymectomy may have a protective effect against neonatal MG. Neonatal MG can cause foetal distress during delivery. Most MG women benefit from being examined by a neurologist during pregnancy, to minimize risks and select the best delivery mode in collaboration with obstetricians.

Fetal arthrogryposis and maternal serum antibodies

Arthrogryposis multiplex congenital (AMC) describes multiple joint contractures resulting from lack of movement in utero. Antibodies directed at the fetal isoform of the muscle acetylcholine receptor (AChR) have been reported in a small number of asymptomatic mothers of AMC babies. We examined sera from 179 mothers of AMC babies and 20 parous and non-parous controls to look for antibodies to AChR or undefined muscle or neuronal proteins. We found positive AChR antibodies in only three sera (1.5%) from asymptomatic AMC mothers. However, there was reactivity with muscle or with neuronal antigens in 33% of the sera, and reactivity to undefined neuronal antigens was more common in sera from mothers of AMC babies with CNS involvement (p=0.001) than those without. The offspring of mothers with AChR antibodies may benefit from treatment during pregnancy. Other maternal antibodies require further study, but these observations add to the emerging literature on maternal antibodies associated with developmental intrauterine disorders.

Escobar syndrome is a prenatal myasthenia caused by disruption of the acetylcholine receptor fetal gamma subunit

Escobar syndrome is a form of arthrogryposis multiplex congenita and features joint contractures, pterygia, and respiratory distress. Similar findings occur in newborns exposed to nicotinergic acetylcholine receptor (AChR) antibodies from myasthenic mothers. We performed linkage studies in families with Escobar syndrome and identified eight mutations within the gamma -subunit gene (CHRNG) of the AChR. Our functional studies show that gamma -subunit mutations prevent the correct localization of the fetal AChR in human embryonic kidney-cell membranes and that the expression pattern in prenatal mice corresponds to the human clinical phenotype. AChRs have five subunits. Two alpha, one beta, and one delta subunit are always present. By switching gamma to epsilon subunits in late fetal development, fetal AChRs are gradually replaced by adult AChRs. Fetal and adult AChRs are essential for neuromuscular signal transduction. In addition, the fetal AChRs seem to be the guide for the primary encounter of axon and muscle. Because of this important function in organogenesis, human mutations in the gamma subunit were thought to be lethal, as they are in gamma -knockout mice. In contrast, many mutations in other subunits have been found to be viable but cause postnatally persisting or beginning myasthenic syndromes. We conclude that Escobar syndrome is an inherited fetal myasthenic disease that also affects neuromuscular organogenesis. Because gamma expression is restricted to early development, patients have no myasthenic symptoms later in life. This is the major difference from mutations in the other AChR subunits and the striking parallel to the symptoms found in neonates with arthrogryposis when maternal AChR auto-antibodies crossed the placenta and caused the transient inactivation of the AChR pathway.

Artrogryposis multiplex congenita -- a rare fetal condition caused by maternal myasthenia gravis

OBJECTIVES

To look at the occurrence of arthrogryposis multiplex congenita in newborn of mothers with myasthenia gravis (MG) and factors connected to this.

MATERIAL AND METHODS

We retrospectively studied 176 births by 79 MG mothers, recorded in the Medical Birth Registry of Norway (MBRN). Four (2.2%) newborns (including one pair of twins) born with severe skeletal anomalies were identified.

RESULTS

All four children died. Three had findings consistent with arthrogryposis multiplexa congenita (AMC), one had a fetal akinesia deformation sequence (FADS). The mother of the child with FADS had previously given birth to a child with neonatal MG. She was now in complete MG remission. The mother of the twins with AMC later gave birth to a child with neonatal MG.

CONCLUSION

Siblings of an affected child -- either with neonatal MG or AMC -- have an increased risk to develop either neonatal MG or AMC. As this appears to be independent of the MG mother's clinical state, it is important to discuss previous pregnancy outcomes with all female MG patients.

Asymptomatic myasthenia gravis influences pregnancy and birth

Women with myasthenia gravis (MG) have an increased risk of complications and adverse pregnancy outcome. This study has examined if this is true also for asymptomatic MG. Using data from the Medical Birth Registry of Norway, births of women prior to receiving an MG diagnosis or in complete clinical MG remission were compared with all non-MG births in Norway in the same period (1967-2000). Forty-nine births occurred in 37 women, 11 of them in clinical remission, and six thymectomized. The perinatal mortality was increased (P = 0.02) and induction of birth (P = 0.007) occurred more frequently. Protracted labor occurred more frequently in the target group (P = 0.03). One of the three children that died had Potter's syndrome. Both mothers with children who died were in complete clinical MG remission. One had previously given and one subsequently gave birth to a child with neonatal MG. The results indicate that complications in birth and pregnancy are not only related to clinical MG disease severity but to the underlying immunological dysfunction.

Antibodies in Myasthenia Gravis and Related Disorders

Acetylcholine receptor (AChR) antibodies are present in around 85% of patients with myasthenia gravis (MG) as measured by the conventional radioimmunoprecipitation assay. Antibodies that block the fetal form of the AChR are occasionally present in mothers who develop MG after pregnancy, especially in those whose babies are born with arthrogryposis multiplex congenita. The antibodies cross the placenta and block neuromuscular transmission, leading to joint deformities and often stillbirth. In these mothers, antibodies made in the thymus are mainly specific for fetal AChR and show restricted germline origins, suggesting a highly mutated clonal response; subsequent spread to involve adult AChR could explain development of maternal MG in those cases who first present after pregnancy. In the 15% of "seronegative" MG patients without AChR antibodies (SNMG), there are serum factors that increase AChR phosphorylation and reduce AChR function, probably acting via a different membrane receptor. These factors are not IgG and could be IgM or even non-Ig serum proteins. In a proportion of SNMG patients, however, IgG antibodies to the muscle-specific kinase, MuSK, are present. These antibodies are not found in AChR antibody-positive MG and are predominantly IgG4. MuSK antibody positivity appears to be associated with more severe bulbar disease that can be difficult to treat effectively.

Antibodies to neuronal targets in neurological and psychiatric diseases

The role of antibodies to specific neuronal and muscle ion channels in the etiology of neuromuscular transmission disorders is now well accepted. In addition, maternal antibodies can cross the placenta and cause neonatal disease or even alter the development of the infant, raising the possibility that some neurodevelopmental conditions could be caused by maternal antibodies. Voltage-gated ion channels are expressed in the brain as well as at the neuromuscular junction, and in recent years it has become clear that antibodies to some central nervous system (CNS) channels can be associated with CNS disease. This review highlights features of these conditions, preliminary investigations into neurodevelopmental disorders, and areas for further study.

Maternal neuronal antibodies associated with autism and a language disorder

Neurodevelopmental disorders could be caused by maternal antibodies or other serum factors. We detected serum antibodies binding to rodent Purkinje cells and other neurons in a mother of three children: the first normal, the second with autism, and the third with a severe specific language disorder. We injected the serum (0.5-1.0 ml/day) into pregnant mice during gestation and found altered exploration and motor coordination and changes in cerebellar magnetic resonance spectroscopy in the mouse offspring, comparing with offspring of mice injected with sera from mothers of healthy children. This evidence supports a role for maternal antibodies in some forms of neurodevelopmental disorder.

Pena-Shokier phenotype: case presentation and review

Pena-Shokier phenotype is an early lethal disorder involving multiple joint contractures, facial anomalies, and pulmonary hypoplasia. Alternative terms for this syndrome used in the literature include fetal hypokinesia syndrome, lethal congenital contracture syndrome, and Pena-Shokier syndrome type I. The etiology for the early cases was attributed to neuromuscular disease, with deformations owing to weakness or paralysis of the motor unit. An abnormality of spinal cord motoneurons has been postulated in some cases. Pena-Shokier phenotype can also result from blockade of the neuromuscular junction, as shown by recent observations with women expressing antibodies against the fetal acetylcholine receptor. It has been shown that the Pena-Shokier phenotype may result from intrauterine cerebral dysfunction as well, including acquired brain insults and congenital brain malformations. The ultimate prognosis for children with this disorder is dependent on the underlying etiology and the severity of pulmonary disease. The authors report a fatal case of Pena-Shokier phenotype with congenital polymicrogyria. To our knowledge, the case presented is the first reported Pena-Shokier phenotype associated with this type of brain malformation.

Long-term survival in a child with arthrogryposis multiplex congenita and spinal muscular atrophy

Spinal muscular atrophy type 0 is a severe form of spinal muscular atrophy that is usually fatal in the first months of life. These children present with arthrogryposis multiplex congenita and respiratory compromise. We describe a child with spinal muscular atrophy and arthrogryposis multiplex congenita who has had a much better course and is alive without ventilator support at age 6 years. This case illustrates that the prognosis for spinal muscular atrophy and arthrogryposis multiplex congenita cannot always be predicted with certainty.

Molecular targets for autoimmune and genetic disorders of neuromuscular transmission

The neuromuscular junction is the target of a variety of autoimmune, neurotoxic and genetic disorders, most of which result in muscle weakness. Most of the diseases, and many neurotoxins, target the ion channels that are essential for neuromuscular transmission. Myasthenia gravis is an acquired autoimmune disease caused in the majority of patients by antibodies to the acetylcholine receptor, a ligand-gated ion channel. The antibodies lead to loss of acetylcholine receptor, reduced efficiency of neuromuscular transmission and muscle weakness and fatigue. Placental transfer of these antibodies in women with myasthenia can cause fetal or neonatal weakness and occasionally severe deformities. Lambert Eaton myasthenic syndrome and acquired neuromyotonia are caused by antibodies to voltage-gated calcium or potassium channels, respectively. In the rare acquired neuromyotonia, reduced repolarization of the nerve terminal leads to spontaneous and repetitive muscle activity. In each of these disorders, the antibodies are detected by immunoprecipitation of the relevant ion channel labelled with radioactive neurotoxins. Genetic disorders of neuromuscular transmission are due mainly to mutations in the genes for the acetylcholine receptor. These conditions show recessive or dominant inheritance and result in either loss of receptors or altered kinetics of acetylcholine receptor channel properties. Study of these conditions has greatly increased our understanding of synaptic function and of disease aetiology.

Teratogen update: maternal myasthenia gravis as a cause of congenital arthrogryposis

BACKGROUND

Arthrogryposis multiplex congenita (AMC) is defined as nonprogressive congenital contractures that generally result from lack of fetal movement in utero. AMC is a feature of many congenital disorders caused by genetic, environmental, or other factors. One rare cause of AMC is maternal myasthenia gravis (MG). This is an autoimmune disorder, caused by antibodies to the nicotinic acetylcholine receptor (AChR), and resulting in weakness of voluntary muscles. In 10-15% of babies born to MG mothers, transient signs of MG are noted after placental transfer of anti-AChR antibodies. In a few cases, AMC predominates.

METHODS

We review the role of antibodies to AChR in MG and in AMC associated with maternal antibodies to AChR.

RESULTS

In anti-AChR antibody-associated AMC, fetal or neonatal death is common; other deformities or CNS abnormalities are common as well. The condition usually recurs in each pregnancy unless the mother is treated for MG, but some mothers are asymptomatic. The maternal antibodies cross the placenta and block the function of the fetal isoform of the AChR leading to fetal paralysis. Injection of maternal plasma into pregnant mice results in AMC in mouse fetuses. Some women with recurrent AMC in their babies have no detectable anti-AChR suggesting the presence of antibodies to other fetal muscle or neuronal proteins.

CONCLUSIONS

Although rare, anti-AChR-associated AMC is potentially treatable and can be diagnosed by a routine antibody test. The mouse model can be used to investigate the role of these and other maternal antibodies in causing congenital conditions.