Congenital hypotonia: systematic approach for prenatal detection.

OBJECTIVES: Congenital hypotonic conditions are rare and heterogeneous, and some are severely debilitating or lethal. Contrary to its prominent postnatal manifestation, the prenatal presentation of hypotonia is frequently subtle, inhibiting prenatal detection. We aimed to characterize the prenatal sonographic manifestation of congenital hypotonia throughout pregnancy, evaluate the yield of diagnostic tests and propose diagnostic models to increase its prenatal detection. METHODS: This was a retrospective observational study of singleton pregnancies with congenital hypotonia, diagnosed either prenatally or immediately after birth, at a single tertiary center between the years 2012 and 2020. Prenatally, hypotonia was diagnosed if a fetus showed sonographic or clinical signs suggestive of hypotonia and had a confirmed underlying genetic condition, or in the absence of a known genetic abnormality if the fetus exhibited multiple prominent signs suggestive of hypotonia. Postnatally, it was diagnosed in neonates displaying reduced muscle tone leading to reduced spontaneous movement, reduced swallowing or feeding difficulty. We reviewed the medical records of pregnant patients carrying fetuses subsequently diagnosed with congenital hypotonia and assessed the yield of ultrasound scans, fetal magnetic resonance imaging, computed tomography and genetic tests. The detection rate of sonographic signs suggesting fetal hypotonia was calculated. The prevalence of non-specific signs, including polyhydramnios, persistent breech presentation, intrauterine growth restriction and maternal perception of reduced fetal movement, were compared between the study group and the local liveborn singleton population. Potential detection rates of different theoretical semiotic diagnostic models, differing in the threshold for referral for a targeted scan, were assessed based on the cohort's data. RESULTS: The study group comprised 26 cases of congenital hypotonia, of which 10 (38.5%) were diagnosed prenatally, and the controls included 95 105 singleton live births, giving a prevalence of congenital hypotonia of 1:3658. Nuchal translucency thickness and the early anomaly scan at 13-17 weeks were normal in all 22 and 23 cases, respectively, in which this was performed. The mid-trimester scan performed at 19-25 weeks was abnormal in four of 24 (16.7%) cases. The overall prenatal detection rate of congenital hypotonic conditions in our cohort was 38.5%. Only cases which underwent a targeted scan were detected and, among the 16 cases which underwent this scan, the prenatal detection rate was 62.5% compared with 0% in pregnancies that did not undergo this scan (P = 0.003). An abnormal genetic diagnosis was obtained in 21 (80.8%) cases using the following modalities: chromosomal microarray analysis (CMA) in two (9.5%), whole-exome sequencing (WES) in 14 (66.7%) and methylation analysis in five (23.8%). CMA was abnormal in 8% (2/25) of the cases and WES detected a causative genetic mutation in 87.5% (14/16) of the cases in which these were performed. Comparison of non-specific signs in the study group with those in the local singleton population showed that hypotonic fetuses had significantly more polyhydramnios (64.0% vs 3.0%, P < 0.0001), persistent breech presentation (58.3% vs 4.2%, P < 0.0001), intrauterine growth restriction (30.8% vs 3.0%, P < 0.0001) and maternal perception of reduced fetal movement (32.0% vs 4.7%, P < 0.0001). Prenatally, the most commonly detected signs supporting a diagnosis of hypotonia were structural anomaly (62.5%, 10/16), reduced fetal movement (46.7%, 7/15), joint contractures (46.7%, 7/15) and undescended testes ≥ 30 weeks (42.9%, 3/7 males). Proposed diagnostic strategies that involved performing a targeted scan for a single non-specific ultrasound sign or two such signs, and then carrying out a comprehensive genetic evaluation for any additional sign, offered theoretical detection rates in our cohort of 88.5% and 57.7%, respectively. CONCLUSIONS: Congenital hypotonic conditions are rare and infrequently detected prenatally. Sonographic signs are visible from the late second trimester. A targeted scan increases prenatal detection significantly. Comprehensive genetic testing, especially WES, is the cornerstone of diagnosis in congenital hypotonia. Theoretical diagnostic models which may increase prenatal detection are provided. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

A nationwide survey of monocarboxylate transporter 8 deficiency in Japan: Its incidence, clinical course, MRI and laboratory findings.

BACKGROUND: Monocarboxylate transporter 8 (MCT8) deficiency is an X-linked recessive developmental disorder characterized by initially marked truncal hypotonia, later athetotic posturing, and severe intellectual disability caused by mutations in SLC16A2, which is responsible for the transport of triiodothyronine (T3) into neurons. We conducted a nationwide survey of patients with MCT8 deficiency to clarify their current status. METHODS: Primary survey: In 2016-2017, we assessed the number of patients diagnosed with MCT8 deficiency from 1027 hospitals. Secondary survey: in 2017-2018, we sent case surveys to 31 hospitals (45 cases of genetic diagnosis), who responded in the primary survey. We asked for: 1) perinatal history, 2) developmental history, 3) head MRI findings, 4) neurophysiological findings, 5) thyroid function tests, and 5) genetic test findings. RESULTS: We estimated the prevalence of MCT8 deficiency to be 1 in 1,890,000 and the incidence of MCT8 deficiency per million births to be 2.12 (95 % CI: 0.99-3.25). All patients showed severe psychomotor retardation, and none were able to walk or speak. The significantly higher value of the free T3/free T4 (fT3/fT4) ratio found in our study can be a simple and useful diagnostic biomarker (Our value 11.60 ± 4.14 vs control 3.03 ± 0.38). Initial white matter signal abnormalities on head MRI showed recovery, but somatosensory evoked potentials (SEP) showed no improvement, suggesting that the patient remained dysfunctional. CONCLUSION: For early diagnosis, including in mild cases, it might be important to consider the clinical course, early head MRI, SEP, and fT3/fT4 ratio.

Fumarase Deficiency: A Case With a New Pathogenic Mutation and a Review of the Literature.

Fumarase deficiency (FD) is a rare and severe autosomal disorder, caused by inactivity of the enzyme fumarase, due to biallelic mutations of the fumarase hydratase (FH) gene. Several pathogenic mutations have been published. The article describes an infant with failure to thrive, microcephaly, axial hypotonia, and developmental retardation with increased excretion of fumarate, no activity of fumarase and a homozygous mutation of the FH gene, which was until recently only known as a variant of unknown significance. Carriers of pathogenic mutations in the FH gene are at risk for developing renal cell carcinoma and should therefore be screened. Both parents were healthy carriers of the mutation and had decreased levels of enzyme activity. In addition, the article presents an overview and analysis of all cases of FD reported thus far in the literature.

Epilepsy and movement disorders in CDG: Report on the oldest-known MOGS-CDG patient.

Congenital glycosylation disorders (CDG) are inherited metabolic diseases due to defective glycoprotein and glycolipid glycan assembly and attachment. MOGS-CDG is a rare disorder with seven patients from five families reported worldwide. We report on a 19-year-old girl with MOGS-CDG. At birth she presented facial dysmorphism, marked hypotonia, and drug-resistant tonic seizures. In the following months, her motility was strongly limited by dystonia, with forced posture of the head and of both hands. She showed a peculiar hyperkinetic movement disorder with a rhythmic and repetitive pattern repeatedly documented on EEG-polygraphy recordings. Brain MRI showed progressive cortical and subcortical atrophy. Epileptic spasms appeared in first months and ceased by the age of 7 years, while tonic seizures were still present at last assessment (19 years). We report the oldest-known MOGS-CDG patient and broaden the neurological phenotype of this CDG.

Prenatal Treatment of Thyroid Hormone Cell Membrane Transport Defect Caused by MCT8 Gene Mutation.

Background: Mutations of the thyroid hormone (TH)-specific cell membrane transporter, monocarboxylate transporter 8 (MCT8), produce an X-chromosome-linked syndrome of TH deficiency in the brain and excess in peripheral tissues. The clinical consequences include brain hypothyroidism causing severe psychoneuromotor abnormalities (no speech, truncal hypotonia, and spastic quadriplegia) and hypermetabolism (poor weight gain, tachycardia, and increased metabolism, associated with high serum levels of the active TH, T3). Treatment in infancy and childhood with TH analogues that reduce serum triiodothyronine (T3) corrects hypermetabolism, but has no effect on the psychoneuromotor deficits. Studies of brain from a 30-week-old MCT8-deficient embryo indicated that brain abnormalities were already present during fetal life. Methods: A carrier woman with an affected male child (MCT8 A252fs268*), pregnant with a second affected male embryo, elected to carry the pregnancy to term. We treated the fetus with weekly 500 µg intra-amniotic instillation of levothyroxine (LT4) from 18 weeks of gestation until birth at 35 weeks. Thyroxine (T4), T3, and thyrotropin (TSH) were measured in the amniotic fluid and maternal serum. Treatment after birth was continued with LT4 and propylthiouracil. Follow-up included brain magnetic resonance imaging (MRI) and neurodevelopmental evaluation, both compared with the untreated brother. Results: During intrauterine life, T4 and T3 in the amniotic fluid were maintained above threefold to twofold the baseline and TSH was suppressed by 80%, while maternal serum levels remained unchanged. At birth, the infant serum T4 was 14.5 µg/dL and TSH <0.01 mU/L compared with the average in untreated MCT8-deficient infants of 5.1 µg/ and >8 mU/L, respectively. MRI at six months of age showed near-normal brain myelination compared with much reduced in the untreated brother. Neurodevelopmental assessment showed developmental quotients in receptive language and problem-solving, and gross motor and fine motor function ranged from 12 to 25 at 31 months in the treated boy and from 1 to 7 at 58 months in the untreated brother. Conclusions: This is the first demonstration that prenatal treatment improved the neuromotor and neurocognitive function in MCT8 deficiency. Earlier treatment with TH analogues that concentrate in the fetus when given to the mother may further rescue the phenotype.

Association between elastography findings of the levator ani and stress urinary incontinence.

PURPOSE: To investigate the elasticity of the levator ani musle (LAM) with the patients suffering from stress urinary incontinence (SUI) by transperineal elastography. METHODS: Conventional transperineal ultrasound and elastography were performed in the patients with SUI on quiescent condition and maximal Valsalva. Transperineal ultrasound and elastography were repeated after Kegel exercises. The scoring system and strain ratio (SR) values were recorded and analyzed. RESULTS: After Kegel exercises, the ratio of subjective improvement or cure was 81 % (102/126). Mean elasticity score (ES) and SR of LAM were significantly higher than the value before on maximal Valsalva, respectively. Mean ES and SR of LAM after Kegel exercises were similar with the value before on quiescent condition, respectively. CONCLUSION: The improvement of SUI was associated with the stiffer LAM assessed by elastography. Women with SUI who have softer LAM were more likely to have symptoms of SUI and Kegel exercise could strengthen the stiffness of LAM. BRIEF SUMMARY: The improvement of SUI was associated with the stiffer LAM assessed by elastography.

Early-onset severe spinocerebellar ataxia 42 with neurodevelopmental deficits (SCA42ND): Case report, pharmacological trial, and literature review.

Early-onset severe spinocerebellar ataxia 42 with neurodevelopmental deficits (SCA42ND, MIM#604065) is an ultrarare autosomal dominant syndrome related to de novo CACNA1G gain-of-function pathogenic variants. All patients with SCA42ND show cerebellar atrophy and/or hypoplasia on neuroimaging and share common features such as dysmorphic features, global developmental delay, and axial hypotonia, all manifesting within the first year of life. To date, only 10 patients with SCA42ND have been reported with functionally confirmed gain-of-function variants, bearing either of two recurrent pathogenic variants. We describe a girl with congenital ataxia, without epilepsy, and a de novo p.Ala961Thr pathogenic variant in CACNA1G. We review the published subjects with the aim of better characterizing the dysmorphic features that may be crucial for clinical recognition of SCA42ND. Cerebellar atrophy, together with digital anomalies, particularly broad thumbs and/or halluces, should lead to clinical suspicion of this disease. We describe the first pharmacological attempt to treat a patient with SCA42ND using zonisamide, an antiepileptic drug with T-type channel blocker activity, in an off-label indication using an itemized study protocol. No efficacy was observed at the dose tested. However, without pharmacological treatment, she showed a positive evolution in neurodevelopment during the follow-up.

A rare cause of syndromic short stature: 3M syndrome in three families.

3M syndrome is a rare autosomal recessive genetic disorder characterized by severe growth retardation, dysmorphic facial features, skeletal dysplasia, and normal intelligence. Variants in CUL7, OBSL1, and CCDC8 genes have been reported to be responsible for this syndrome. In this study, the clinical and molecular findings of four 3M syndrome cases from three families are presented. All cases had growth retardation, relative macrocephaly, and typical dysmorphic facial features. Their neurological developments were normal. Sequencing of CUL7, OBSL1, and CCDC8 genes revealed two different novel homozygous variants in CUL7 in Families 1 and 3 and a previously reported homozygous pathogenic variant in OBSL1 in Family 2. In conclusion, a comprehensive dysmorphological evaluation should be obtained in individuals presenting with short stature and in such individuals with typical facial and skeletal findings, 3M syndrome should be considered. Our report expands the genotype of 3M syndrome and emphasizes the importance of thorough physical and dysmorphological examination.

Three M syndrome 2 in two Indian patients.

3-M syndrome is a rare autosomal recessive disorder, characterized by short stature, characteristic facies and absence of microcephaly and intellectual disability. 3-M syndrome 2 (MIM# 612921) is caused by biallelic disease causing variants in OBSL1. In this study, we identified two probands from two families with homozygous, c.1534 + 5G > T and compound heterozygous variants, c.35dup and c.1273dup in OBSL1, respectively. We herein highlight the clinical and molecular findings of the first reported cases from Indian ethnicity.

Homozygous frameshift mutation of SPG11 as a cause of progressive flaccid paralysis, ataxia and dysphagia.

Hereditary spastic paraplegias (HSP) are phenotypically and genotypically diverse. We describe a unique case of autosomal recessive HSP (ARHSP) diagnosed at age 44 in a patient previously described as having "spinal muscular ataxia" [sic]. Predominant lower motor neuron findings and lack of clinical spasticity reduced suspicion for HSP in early life. The identified SPG11 mutation was novel and the presentation was atypical for HSP in general and SPG11 disease specifically.

Neurological phenotype of Potocki-Lupski syndrome.

Potocki-Lupski syndrome is a condition mainly characterized by infantile hypotonia, developmental delay/intellectual disability (DD/ID), and congenital anomalies, caused by duplications of the 17p11.2 region, encompassing RAI1 gene. Its clinical presentation is extremely variable, especially for what concerns the cognitive level and the behavioral phenotype. Such aspects, as well as the dysmorphic/malformative ones, have been covered by previous studies; otherwise neurological features have never been systematically described. In order to delineate the neurological phenotype of Potocki-Lupski Syndrome, we collect an 8-patients cohort. Developmental milestones are delayed and a mild to moderate cognitive impairment is present in all patients, variably associated with features of autism spectrum disorder, behavioral disturb, and sleep disturb. Hypotonia appears a less frequent finding than what previously reported, while motor clumsiness/coordination impairment is frequent. EGG registration demonstrated a common pattern with excess of diffuse rhythmic activity in sleep phases or while the patient is falling asleep. Brain MRI did not reveal common anomalies, although unspecific white matter changes may be present. We discuss such findings and compare them to literature data, offering an overview on the neurological and cognitive-behavioral presentation of the syndrome.

Microcephaly, Hypotonia, and Intracranial Calcifications in an 11-Week-Old Boy.

An 11-week-old unvaccinated, term Amish boy initially presented with poor feeding, microcephaly, failure to thrive, and developmental delays. His physical examination was significant for both weight and head circumference being less than the third percentile, and he was noted to have micrognathia, truncal hypotonia, and head lag. He was admitted to the pediatric hospital medicine service for further diagnostic evaluation. Laboratory studies assessing for endocrinological and metabolic etiologies yielded negative results, and imaging studies (including a chest radiograph, echocardiogram, and abdominal ultrasound) were normal. However, intracranial calcifications were noted on a head ultrasound. The etiology of his constellation of symptoms was initially thought to be infectious, but the ultimate diagnosis was not made until after discharge from the pediatric hospital medicine service.

A novel homozygous nonsense mutation of VPS13B associated with previously unreported features of Cohen syndrome.

Cohen syndrome (CS) is a rare autosomal recessive disorder associated with mutations in the vacuolar protein sorting 13 homolog B (VPS13B; formerly COH1) gene. The core clinical phenotype comprises a characteristic facial gestalt, marked developmental delay, and myopia. Additional, nonobligatory features include obesity, microcephaly, short stature, muscular hypotonia, scoliosis, narrow hands and feet, progressive retinopathy, as well as neutropenia. Here we report a novel homozygous nonsense mutation in the VPS13B gene and previously undescribed clinical features in a 19-year-old woman with developmental delay, intellectual disability, and a particular facial appearance. The patient showed several features consistent with CS. In addition, the parents observed congenital alacrima and anhidrosis persisting until onset of puberty. The diagnosis was not established based on the clinical phenotype. We performed whole-genome sequencing and identified a novel homozygous nonsense mutation c.62T>G (NM_152564.4), p.(Leu21*) in the VPS13B gene. Our findings extended the previously reported phenotype of CS. We conclude that transient, prepubertal alacrima and anhidrosis are part of the phenotypic spectrum of CS associated with a novel homozygous nonsense mutation in the VPS13B gene.

Brain white matter abnormalities associated with copy number variants.

White matter (WM) signal abnormalities are demonstrated in various neurodevelopmental disorders on brain magnetic resonance imaging (MRI). The pattern of WM abnormalities can aid in the diagnostic process. This study aims to characterize the WM changes found in microdeletion/microduplication syndromes. Thirteen patients with neurodevelopmental disorders due to copy number variations were collected from a cohort of children with evidence of WM abnormalities on brain MRI, in two medical centers. A pediatric neuroradiologist blindly interpreted the MRI scans. Clinical and genetic findings were retrospectively extracted from the medical records. WM changes included: multifocal (10/13) periventricular (12/13) and subcortical (5/13) signal abnormalities and WM volume loss (6/13). Dysgenesis of the corpus callosum was depicted in 12/13. The main clinical features were: global developmental delay (13/13), hypotonia (11/13), epilepsy (10/13), dysmorphic features (9/13), microcephaly (6/13), short stature (6/13), and systemic involvement (6/13). We showed that different chromosomal micro-rearrangement syndromes share similar MRI patterns of nonspecific multifocal predominantly periventricular WM changes associated with corpus callosum dysgenesis with or without WM and gray matter loss. Hence, the association of these features in a patient evaluated for global developmental delay/intellectual disability suggests a chromosomal micro-rearrangement syndrome, and a chromosomal microarray analysis should be performed.

Novel mutations in SLC16A2 associated with a less severe phenotype of MCT8 deficiency.

Mutations in the thyroid hormone transporter MCT8 cause severe intellectual and motor disability and abnormal serum thyroid function tests, a syndrome known as MCT8 deficiency (or: Allan-Herndon-Dudley syndrome, AHDS). Although the majority of patients are unable to sit or walk independently and do not develop any speech, some are able to walk and talk in simple sentences. Here, we report on two cases with such a less severe clinical phenotype and consequent gross delay in diagnosis. Genetic analyses revealed two novel hemizygous mutations in the SLC16A2 gene resulting in a p.Thr239Pro and a p.Leu543Pro substitution in the MCT8 protein. In vitro studies in transiently transfected COS-1 and JEG-3 cells, and ex vivo studies in patient-derived fibroblasts revealed substantial residual uptake capacity of both mutant proteins (Leu543Pro > Thr239Pro), providing an explanation for the less severe clinical phenotype. Both mutations impair MCT8 protein stability and interfere with proper subcellular trafficking. In one of the patients calcifications were observed in the basal ganglia at the age of 29 years; an abnormal neuroradiological feature at this age that has been linked to untreated (congenital) hypothyroidism and neural cretinism. Our studies extend on previous work by identifying two novel pathogenic mutations in SLC16A2 gene resulting in a mild clinical phenotype.

Nonleaking cystoid macular edema in Cohen syndrome.

An 11-year-old girl with a history of neutropenia, developmental delay, hypotonia, and intellectual disability was diagnosed with Cohen syndrome after genetic testing discovered homozygous mutation in the VPS13B gene. She was referred to a retinal specialist with a chief complaint of decreased peripheral vision. On examination, decreased visual acuity, pigmentary changes, and nonleaking cystoid macular edema were present in both eyes.

A Very Rare Etiology of Hypotonia and Seizures: Congenital Glutamine Synthetase Deficiency.

Mutations in the human GLUL gene, which encodes the enzyme glutamine synthetase (GS), may cause congenital glutamine synthetase deficiency. The disease was first described in 2005 and only three patients have been reported to date. We report a fourth patient suffering from congenital GS deficiency who was found to have some distinctive clinical findings. The patient was a 30-month-old girl who was referred to us due to developmental delay and seizures which began at 5 months of age. She was seizure free for 5 months with valproic acid and vigabatrin. At presentation, she was found to have microcephaly and hypotonia. Her plasma glutamine concentration was near normal and she had mild hyperammonemia. Cranial magnetic resonance imaging (MRI) showed mild changes. Whole exome sequencing (WES) revealed a homozygous c.121C > T (p.R41C) (p.Arg41Cys) pathogenic variant of the GLUL gene. The diagnosis of this patient underlines the importance of careful evaluation of patients with borderline low glutamine levels. Treatment was begun with L-glutamine and nicotinamide and biochemical improvements have been observed at 6 months of follow-up. The outcome of this patient may provide important data about the effectiveness of glutamine and nicotinamide treatment in patients with congenital GS deficiency.

Prenatal and postnatal presentation of PRMT7 related syndrome: Expanding the phenotypic manifestations.

Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyze the transfer of methyl groups from S-adenosyl-l-methionine to nitrogen atoms on arginine residues. Arginine methylation is involved in multiple biological processes, such as signal transduction, mRNA splicing, transcriptional control, DNA repair, and protein translocation. Currently, 10 patients have been described with mutations in PRMT7. The shared findings include: hypotonia, intellectual disability, short stature, brachydactyly, and mild dysmorphic features. We describe the prenatal, postnatal, and pathological findings in two male sibs homozygote for a mutation in PRMT7. Both had intrauterine growth restriction involving mainly the long bones. In addition, eye tumor was found in the first patient, and nonspecific brain calcifications and a systemic venous anomaly in the second. The pregnancy of the first child was terminated and we describe the autopsy findings. The second child had postnatal growth restriction of prenatal onset, hypotonia, strabismus, sensorineural hearing loss, genitourinary and skeletal involvement, and global developmental delay. He had dysmorphic features that included frontal bossing, upslanting palpebral fissures, small nose with depressed nasal bridge, and pectus excavatum. Our patients provide additional clinical and pathological data and expand the phenotypic manifestations associated with PRMT7 homozygote/compound heterozygote mutations to include brain calcifications and delayed myelination, and congenital orbital tumor.

Adenosine Kinase Deficiency: Report and Review.

Adenosine kinase (ADK) deficiency (OMIM [online mendelian inheritance in man]: 614300) is an autosomal recessive disorder of adenosine and methionine metabolism, with a unique clinical phenotype, mainly involving the central nervous system and dysmorphic features. Patients usually present early in life with sepsis-like symptoms, respiratory difficulties, and neonatal jaundice. Subsequently, patients demonstrate hypotonia and global developmental delay. Biochemically, methionine is elevated with normal homocysteine levels and the diagnosis is confirmed through molecular analysis of the ADK gene. There is no curative treatment; however, a methionine-restricted diet has been tried with variable outcomes. Herein, we report a 4-year-old Saudi female with global developmental delay, hypotonia, and dysmorphic features. Interestingly, she has a tall stature, developmental dysplasia of the hip, optic nerve gliosis, and tigroid fundus. We found a mutation not reported previously and we compared the current case with previously reported cases. We alert clinicians to consider ADK deficiency in any neonate presenting with global developmental delay, hypotonia, dysmorphic features, and high methionine levels.