Novel CAD gene mutations in a boy with developmental and epileptic encephalopathy 50 with dramatic response to uridine therapy: a case report and a review of the literature.

BACKGROUND: Developmental and epileptic encephalopathy-50 (DEE-50) is a rare clinical condition believed to be caused by a mutation in the CAD gene and is associated with a bleak prognosis. CAD-related diseases have a wide range of clinical manifestations and other symptoms that may be easily overlooked. Like other rare diseases, the clinical manifestations and the treatment of DEE-50 necessitate further investigation. CASE PRESENTATION: A 1-year-old male patient presented with developmental delay, seizures, and anaemia at 3 months of age. He further developed refractory status epilepticus (SE), rapid deterioration of cognitive and motor function, and even became comatose at 5 months of age. Whole-exome sequencing of trios (WES-trios) revealed a compound heterozygous variant in the CAD gene, with one locus inherited from his father (c.1252C>T: p.Q418* nonsense mutation) and one from his mother (c.6628G>A: p.G2210S, missense mutation). This compound heterozygous CAD variant was unreported in the Human Gene Mutation Database. After uridine treatment, his cognitive faculties dramatically improved and he remained seizure-free. Forty two cases with CAD gene mutation reported in the literatures were reviewed. Among them, 90% had onset before 3 years of age, with average of 1.6±1.8 years old. The average age of diagnosis was 7.7 ± 10 years. The mortality rate was approximately 9.5%, with all reported deaths occurring in patients without uridine treatment. The clinical entity could be improved dramatically when the patient treated with uridine. CONCLUSIONS: We present a boy with DEE 50 caused by novel CAD gene mutations and reviewed the clinical features of 42 patients reported previously. DEE 50 has early onset, refractory seizures, even status epilepticus leading to death, with favorable response to treatment with oral uridine. Early uridine treatment is recommended if CAD defect is suspected or genetically diagnosed. This study enhances the knowledge of DEE 50 and expands the spectrum of CAD gene mutations.

Prevalence of DDC genotypes in patients with aromatic L-amino acid decarboxylase (AADC) deficiency and in silico prediction of structural protein changes.

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare autosomal recessive genetic disorder affecting the biosynthesis of dopamine, a precursor of both norepinephrine and epinephrine, and serotonin. Diagnosis is based on the analysis of CSF or plasma metabolites, AADC activity in plasma and genetic testing for variants in the DDC gene. The exact prevalence of AADC deficiency, the number of patients, and the variant and genotype prevalence are not known. Here, we present the DDC variant (n = 143) and genotype (n = 151) prevalence of 348 patients with AADC deficiency, 121 of whom were previously not reported. In addition, we report 26 new DDC variants, classify them according to the ACMG/AMP/ACGS recommendations for pathogenicity and score them based on the predicted structural effect. The splice variant c.714+4A>T, with a founder effect in Taiwan and China, was the most common variant (allele frequency = 32.4%), and c.[714+4A>T];[714+4A>T] was the most common genotype (genotype frequency = 21.3%). Approximately 90% of genotypes had variants classified as pathogenic or likely pathogenic, while 7% had one VUS allele and 3% had two VUS alleles. Only one benign variant was reported. Homozygous and compound heterozygous genotypes were interpreted in terms of AADC protein and categorized as: i) devoid of full-length AADC, ii) bearing one type of AADC homodimeric variant or iii) producing an AADC protein population composed of two homodimeric and one heterodimeric variant. Based on structural features, a score was attributed for all homodimers, and a tentative prediction was advanced for the heterodimer. Almost all AADC protein variants were pathogenic or likely pathogenic.

CAG Repeat Expansion in THAP11 Is Associated with a Novel Spinocerebellar Ataxia.

BACKGROUND: More than 50 loci are associated with spinocerebellar ataxia (SCA), and the most frequent subtypes share nucleotide repeats expansion, especially CAG expansion. OBJECTIVE: The objective of this study was to confirm a novel SCA subtype caused by CAG expansion. METHODS: We performed long-read whole-genome sequencing combined with linkage analysis in a five-generation Chinese family, and the finding was validated in another pedigree. The three-dimensional structure and function of THAP11 mutant protein were predicted. Polyglutamine (polyQ) toxicity of THAP11 gene with CAG expansion was assessed in skin fibroblasts of patients, human embryonic kidney 293 and Neuro-2a cells. RESULTS: We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects. Among the patients, the number of CAA interruptions within CAG repeats was decreased to 3 (up to 5-6 in controls), whereas the number of 3' pure CAG repeats was up to 32 to 87 (4-16 in controls), suggesting that the toxicity of polyQ protein was length dependent on the pure CAG repeats. Intracellular aggregates were observed in cultured skin fibroblasts from patients. THAP11 polyQ protein was more intensely distributed in the cytoplasm of cultured skin fibroblasts from patients, which was replicated with in vitro cultured neuro-2a transfected with 54 or 100 CAG repeats. CONCLUSIONS: This study identified a novel SCA subtype caused by intragenic CAG repeat expansion in THAP11 with intracellular aggregation of THAP11 polyQ protein. Our findings extended the spectrum of polyQ diseases and offered a new perspective in understanding polyQ-mediated toxic aggregation. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

MECP2 germline mosaicism plays an important part in the inheritance of Rett syndrome: a study of MECP2 germline mosaicism in males.

BACKGROUND: Germline mosaicisms could be inherited to offspring, which considered as "de novo" in most cases. Paternal germline MECP2 mosaicism has been reported in fathers of girls with Rett syndrome (RTT) previously. For further study, we focused on MECP2 germline mosaicism in males, not only RTT fathers. METHODS: Thirty-two fathers of RTT girls with MECP2 pathogenic mutations and twenty-five healthy adult males without history and family history of RTT or other genetic disorders were recruited. Sperm samples were collected and ten MECP2 hotspot mutations were detected by micro-droplet digital PCR (mDDPCR). And routine semen test was performed at the same time if the sample was sufficient. Additionally, blood samples were also detected for those with sperm MECP2 mosaicisms. RESULTS: Nine fathers with RTT daughters (28.1%, 9/32) were found to have MECP2 mosaicism in their sperm samples, with the mutant allele fractions (MAFs) ranging from 0.05% to 7.55%. Only one father with MECP2 c.806delG germline mosaicism (MAF 7.55%) was found to have mosaicism in the blood sample, with the MAF was 0.28%. In the group of healthy adult males, MECP2 mosaicism was found in 7 sperm samples (28.0%, 7/25), with the MAFs ranging from 0.05% to 0.18%. None of the healthy adult males with MECP2 germline mosaicisms were found with MECP2 mosaicism in blood samples. There were no statistical differences in age, or the incidence of asthenospermia between fathers with RTT daughters and healthy adult males with MECP2 germline mosaicisms. Additionally, there was no linear correlation between MAFs of MECP2 mosaicisms and the age of males with germline MECP2 mosaicisms. CONCLUSIONS: Germline MECP2 mosaicism could be found not only in fathers with RTT daughters but also in healthy adult males without family history of RTT. As germline mosaic mutations may be passed on to offspring which commonly known as "de novo", more attention should be paid to germline mosaicism, especially in families with a proband diagnosed with genetic disorders.

Ultrasound-guided interlaminar approach for nusinersen administration in patients with spinal muscular atrophy with spinal fusion or severe scoliosis.

BACKGROUND: Intrathecal injection of medications can be challenging in spinal muscular atrophy (SMA) patients with severe scoliosis or after spine surgery. Here we report our experience with real-time ultrasound (US)-guided intrathecal administration of nusinersen in patients with SMA. METHODS: Seven patients (six children and one adult) with either spinal fusion or severe scoliosis were enrolled. We performed intrathecal injections of nusinersen under US guidance. The efficacy and safety of US-guided injection were explored. RESULTS: Five patients had undergone spinal fusion, while the other two presented severe scoliosis. Success was achieved in 19/20 lumbar punctures (95%), 15 of which were performed through the near-spinous process approach. The intervertebral space with a designated channel was selected for the five postoperative patients, while the interspaces with the smallest rotation angle were chosen for the other two patients with severe scoliosis. In 89.5% (17/19) of the punctures, the number of insertions was no more than two. No major adverse events were observed. CONCLUSION: Given its safety and efficacy, real-time US guidance is recommended for SMA patients with spine surgery or severe scoliosis, and the near-spinous process view can be used as a interlaminar puncture approach for US guidance.

Clinical and genetic spectrum of hereditary spastic paraplegia in Chinese children.

AIM: To explore the clinical and genetic spectrum of hereditary spastic paraplegia (HSP) in Chinese children. METHOD: This retrospective study was conducted between January 2014 and October 2021 in children clinically diagnosed with either pure HSP (pHSP) or complex HSP (cHSP). RESULTS: We investigated 45 children (32 males, 13 females; mean age [SD] at symptom onset 4 years [7 months]). clinically diagnosed with HSP and identified genetic causes in 35 patients. Most patients with autosomal dominant HSP had pHSP (16/18), whereas most patients with autosomal recessive HSP tended to have cHSP (14/16). SPG11 was the most common autosomal recessive subtype, followed by FA2H/SPG35, whereas SPAST/SPG4 was the most frequent cause of autosomal dominant HSP. Two patients with CPT1C mutations presented with a complex phenotype. Meanwhile, 10 patients were found to have likely pathogenic variants/variants of uncertain clinical significance in six genes related to HSP. INTERPRETATION: SPG11 and SPG4 were the most frequent subtypes in Chinese children with autosomal recessive HSP and autosomal dominant HSP. However, the prevalence of SPG4 was much lower than that in adults, which might be explained by the late onset of the disease. On the other hand, FA2H/SPG35 was common in our cohort, while it contributed to only a small proportion of adult cases, which might be explained by its rapid progression and early death in some patients. We also expanded the genetic and clinical spectra of SPG73.

Juvenile Generalized Myasthenia Gravis With AChR and MuSK Antibody Double Positivity: A Case Report With a Review of the Literature.

Myasthenia gravis is an autoimmune disease mediated by B cells and is associated with acetylcholine receptor (AChR) and muscle-specific receptor tyrosine kinase (MuSK) antibodies in the postsynaptic membrane at the neuromuscular junction. The presence of both antibodies in the serum of patients with myasthenia gravis has been rarely reported. Case description: A 9-year-old girl was admitted to our hospital with the chief complaints of reduced facial expression for 3 months and unclear speech and choking from drinking water for 2 months. The diagnosis of generalized myasthenia gravis was made based on clinical manifestations, repetitive electrical nerve stimulation, neostigmine tests, specific antibody tests and other auxiliary examinations. We found the rare coexistence of two key antibodies (anti-AChR and anti-MuSK antibodies) in the patient's serum. The patient experienced myasthenic crisis and received respiratory support even though she was taking prednisone therapy. Due to the poor response to treatment with pyridostigmine bromide, glucocorticoids and IVIG, we administered rituximab therapy, and she responded well and achieved clinical remission. This suggests that clinicians should pay more attention to atypical cases and antibody detection. Rituximab should be considered when conventional treatment fails.

Mitochondrial DNA Copy Number in Rett Syndrome Caused by Methyl-CpG-Binding Protein-2 Variants.

OBJECTIVE: To determine changes in mitochondrial DNA (mtDNA) copy number in peripheral blood in Rett syndrome caused by methyl-CpG-binding protein-2 (MECP2) variants and explore the mechanism of mitochondrial dysfunction in Rett syndrome. STUDY DESIGN: Female patients who were diagnosed with Rett syndrome and had an MECP2 variant (n = 142) were recruited in this study, along with the same number of age- and sex-matched healthy controls. MtDNA copy number was quantified by real-time quantitative polymerase chain reaction with TaqMan probes. The differences in mtDNA copy number between the Rett syndrome group and the control group were analyzed using the independent-samples t test. Linear regression, biserial correlation analysis, and one-way ANOVA were applied for the correlations between mtDNA copy number and age, clinical severity, variant types, functional domains, and hot-spot variants. RESULTS: MtDNA copy number was found to be significantly increased in the patients with Rett syndrome with MECP2 gene variants compared with the control subjects. Age, clinical severity, variant types, functional domains, and hot-spot variants were not related to mtDNA copy number in patients with Rett syndrome. CONCLUSIONS: MtDNA copy number is increased significantly in patients with Rett syndrome, suggesting that changes in mitochondrial function in Rett syndrome trigger a compensatory increase in mtDNA copy number and providing new possibilities for treating Rett syndrome, such as mitochondria-targeted therapies.

A novel homozygous SLC39A14 variant in an infant with hypermanganesemia and a review of the literature.

Background: Manganese (Mn) is an essential trace metal necessary for good health; however, excessive amounts in the body are neurotoxic. To date, three genes (SLC30A10, SLC39A8, and SLC39A14) have been discovered to cause inborn errors in Mn metabolism in humans. As very rare diseases, the clinical features require further clarification. Methods: A male Chinese patient who mainly presented with hypermanganesemia and progressive parkinsonism-dystonia was recruited for this study. We collected and analyzed clinical information, performed whole-exome sequencing (WES), and reviewed the relevant literature. Results: The motor-developmental milestones of the patient were delayed at the age of 4 months, followed by rapidly progressive dystonia. The patient displayed elevated Mn concentrations in blood and urine, and brain magnetic resonance imaging (MRI) showed symmetrical hyperintensity on T1-weighted images and hypointensity on T2-weighted images in multiple regions. A novel homozygous variant of the SLC39A14 gene (c.1058T > G, p.L353R) was identified. The patient was treated with disodium calcium edetate chelation (Na2CaEDTA). Three months later, mild improvement in clinical manifestation, blood Mn levels, and brain MRI was observed. To date, 15 patients from 10 families have been reported with homozygous mutations of SLC39A14, with a mean age of onset of 14.9 months. The common initial symptom is motor regression or developmental milestone delay, with a disease course for nearly all patients involving development of progressive generalized dystonia and loss of ambulation before treatment. Additionally, hypermanganesemia manifests as Mn values ranging from 4- to 25-fold higher than normal baseline levels, along with brain MRI results similar to those observed in the recruited patient. Nine SLC39A14 variants have been identified. Seven patients have been treated with Na2CaEDTA, and only one patient achieved obvious clinical improvement. Conclusion: We identified a novel SLC39A14 mutation related to autosomal recessive hypermanganesemia with dystonia-2, which is a very rare disease. Patients present motor regression or delay of developmental milestones and develop progressive generalized dystonia. Chelation therapy with Na2CaEDTA appears to effectively chelate Mn and increase urinary Mn excretion in some cases; however, clinical response varies. The outcome of the disease was unsatisfactory. This study expands the genetic spectrum of this disease.