Variants located in intron 6 of SMN1 lead to misdiagnosis in genetic detection and screening for SMA.

Accurate genetic diagnosis is necessary for guiding the treatment of spinal muscular atrophy (SMA). An updated consensus for the diagnosis and management of SMA was published in 2018. However, clinicians should remain alert to some pitfalls of genetic testing that can occur when following a routine diagnosis. In this study, we report the diagnosis of three unrelated individuals who were initially misdiagnosed as carrying a homozygous deletion of SMN1 exon 7. MLPA (P060 and P021) and qPCR were used to detect the copy number of SMN. SMN1 variants were identified by SMN1 clone and next-generation sequencing (NGS). Transcription of SMN1 variants was detected using qRT-PCR and ex vivo splicing analysis. Among the three individuals, one was identified as a patient with SMA carrying a heterozygous deletion and a pathogenic variant (c.835-17_835-14delCTTT) of SMN1, one was a healthy carrier only carrying a heterozygous deletion of SMN1 exon 7, and the third was a patient with nemaline myopathy 2 carrying a heterozygous deletion of SMN1 exon 7. The misdiagnosis of these individuals was attributed to the presence of the c.835-17_835-14delCTTT or c.835-17C > G variants in SMN1 intron 6, which affect the amplification of SMN1 exon 7 during MLPA-P060 and qPCR testing. However, MLPA-P021 and NGS analyses were unaffected by these variants. These results support that additional detection methods should be employed in cases where the SMN1 copy number is ambiguous to minimize the misdiagnosis of SMA.

[Clinical features of children with febrile seizures caused by Omicron variant infection]. / Omicronå˜å¼‚æ ªæ„ŸæŸ“å¯¼è‡´å„¿ç«¥çƒ­æ€§æƒŠåŽ¥çš„ä¸´åºŠç‰¹å¾åˆ†æž.

OBJECTIVES: To study the clinical features of children with febrile seizures after Omicron variant infection. METHODS: A retrospective analysis was performed on the clinical data of children with febrile seizures after Omicron variant infection who were admitted to the Department of Neurology, Children's Hospital Affiliated to the Capital Institute of Pediatrics, from December 1 to 31, 2022 (during the epidemic of Omicron variant; Omicron group), and the children with febrile seizures (without Omicron variant infection) who were admitted from December 1 to 31, in 2021 were included as the non-Omicron group. Clinical features were compared between the two groups. RESULTS: There were 381 children in the Omicron group (250 boys and 131 girls), with a mean age of (3.2±2.4) years. There were 112 children in the non-Omicron group (72 boys and 40 girls), with a mean age of (3.5±1.8) years. The number of children in the Omicron group was 3.4 times that in the non-Omicron group. The proportion of children in two age groups, aged 1 to <2 years and 6-10.83 years, in the Omicron group was higher than that in the non-Omicron group, while the proportion of children in two age groups, aged 4 to <5 years and 5 to <6 years, was lower in the Omicron group than that in the non-Omicron group (P<0.05).The Omicron group had a significantly higher proportion of children with cluster seizures and status convulsion than the non-Omicron group (P<0.05). Among the children with recurrence of febrile seizures, the proportion of children aged 6-10.83 years in the Omicron group was higher than that in the non-Omicron group, while the proportion of children aged 3 years, 4 years, and 5 years in the Omicron group was lower than that in the non-Omicron group (P<0.05). CONCLUSIONS: Children with febrile seizures after Omicron variant infection tend to have a wider age range, with an increase in the proportion of children with cluster seizures and status convulsion during the course of fever.

Novel Alu-mediated deletions of the SMN1 gene were identified by ultra-long read sequencing technology in patients with spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by biallelic variants of the survival motor neuron 1 (SMN1) gene. In this study, our aim was to make a molecular diagnosis in two patients with SMA carrying only one SMN1 copy number. Using ultra-long read sequencing (Ultra-LRS), 1415 bp deletion and 3348 bp deletion of the SMN1 gene were identified in patient 1 and the father of patient 2, respectively. Ultra-LRS revealed two novel deletions, starting from the SMN1 promoter to intron 1. It also accurately provided the location of the deletion breakpoints in the SMN1 gene: chr5 g.70,924,798-70,926,212 for a 1415 bp deletion; chr5 g.70,922,695-70,926,042 for a 3348 bp deletion. By analyzing the breakpoint junctions, we identified that these genomic sequences were composed of Alu sequences, including AluJb, AluYm1, AluSq, and AluYm1, indicating that Alu-mediated rearrangements are a mechanism of SMN1 deletion events. In addition, full-length SMN1 transcripts and SMN protein in patient 1 were significantly decreased (p < 0.01), suggesting that a 1415 bp deletion that included the transcription and translation initiation sites of the SMN1 gene had severe consequences for SMN expression. Ultra-LRS can easily distinguish highly homozygous genes compared to other detection technologies, which is useful for detecting SMN1 intragenic mutations, to quickly discover structural rearrangements and to precisely present the breakpoint positions.

Antisense oligonucleotides targeting the SMN2 promoter region enhance SMN2 expression in spinal muscular atrophy cell lines and mouse model.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by homozygous deletions or mutations in survival motor neuron gene 1 (SMN1). Currently, the primary therapeutic strategy for SMA is to increase the level of SMN via correcting SMN2 splicing (nusinersen and risdiplam). However, some patients with SMA do not respond to such treatments, thereby warranting a need to develop new therapeutic strategies. We have previously reported that SMN2 expression is epigenetically regulated by DNA methylation levels of the SMN2 promoter region. In the present study, we determined that methyl-CpG-binding protein 2 (MeCP2) may bind to this critical promoter region (nt-167 to 43). Antisense oligonucleotides (ASO-P1 and ASO-P2) were designed to target the key methylation sites in the SMN2 promoter region, which enhanced the overall transcription and functional protein expression levels in the SMA cell lines. These results were similar to those observed in nusinersen-treated SMA cells. Moreover, a combined treatment of ASO-P1 and ASO-NUS in SMA cell lines further increases fl-SMN2 transcript and SMN protein levels. The delivery of ASO-P1 to the central nervous system of severe SMA mice corrected the molecular, pathological, and functional phenotypes of this disease and increased survival rates. Our findings suggest that the key methylation regions in the SMN2 promoter region may be a novel therapeutic target for SMA.

Bone mineral density and its influencing factors in Chinese children with spinal muscular atrophy types 2 and 3.

BACKGROUND: Patients with spinal muscular atrophy (SMA) are at risk of decreased bone mineral density (BMD). The bone health status of Chinese patients with SMA has been poorly studied. We aimed to evaluate the BMD of children with SMA types 2 and 3 in mainland China and investigate its influencing factors. METHODS: Forty patients with a mean age of 5.5 years affected by SMA types 2 and 3 (n = 22 and n = 18, respectively) were enrolled between September 2017 and May 2019. Total body less head (TBLH) BMD, lumbar spine (LS) BMD, and body composition were measured using dual-energy X-ray absorptiometry (DXA). Serum bone metabolism markers and complete spinal radiographs were assessed. We utilized a linear regression model to explore the correlations between BMD and its related factors. RESULTS: A total of 67.5% (27/40) of patients were diagnosed with low BMD and 2.5% (1/40) were diagnosed with osteoporosis. The TBLH BMD and LS BMD Z-scores in children with SMA type 2 were significantly lower than those with SMA type 3. Both TBLH and LS BMD Z-scores tended to increase with the change of SMA subtypes from 2a-3b. Vitamin D insufficiency and deficiency were found in 37.5% (15/40) of the patients. Serum Ca, phosphorus (P), alkaline phosphatase (ALP) and parathormone (PTH) levels were normal. There were no significant differences among the four subtypes in terms of all the serum bone metabolism markers. Phenotype was significantly associated with TBLH BMD and LS BMD Z-scores, and serum PTH levels were significantly associated with TBLH BMD Z-scores. CONCLUSIONS: Low BMD and osteoporosis were highly prevalent in mainland Chinese children with SMA types 2 and 3. Phenotype and serum PTH level might be the influencing factors of BMD. Regular monitoring of BMD by DXA scan and taking active interventions aim to SMA children with different types are important.

Factors associated with delayed diagnosis of spinal muscular atrophy in China and changes in diagnostic delay.

Spinal muscular atrophy (SMA) is a rare neuromuscular disease, which often occurs in childhood. Early SMA treatment may be highly beneficial to SMA patients, their families, and society. However, delayed diagnosis is common. To identify the factors that affect the SMA diagnostic time window, we analyzed disease characteristics, family factors, and medical factors of 205 SMA families. We compared the data with those of our previous cohort to explore the dynamic changes in the diagnostic time window. The median diagnostic time windows for SMA types I, II, and III were 3.38 [interquartile range (IQR): 2.01-4.98], 4.08 (IQR: 2.07-8.17), and 11.37 (IQR: 4.92-24.07) months, respectively. The diagnostic time window in patients who were clinically diagnosed with SMA at their first hospital visit was 49.42% shorter than that in other patients. Type I/II patients visited approximately 2.56 doctors before diagnosis, while type III patients visited approximately 3.94 doctors before diagnosis. The diagnostic time windows for types II and III were 54.67 and 62.10% shorter, respectively, than those in the previous cohort, which is mainly due to improvements in medical capacity. Therefore, with public awareness, increased medical personnel understanding, and increased neonatal screening, the SMA diagnostic time window is expected to further reduce.

Hydrocephalus due to aqueductal stenosis presenting with acute bilateral ptosis: case report.

Hydrocephalus may cause Parinaud's syndrome which consists of vertical gaze palsy, convergence palsy, lid retraction and pupil light-near dissociation. We are aware of only two prior reports of hydrocephalus presenting with bilateral ptosis. Both were cured by ventriculoperitoneal shunts. We report a 28-month-old girl who presented acute bilateral ptosis but full eye movements both sides. Neuroimages revealed chronic hydrocephalus and aqueductal stenosis. The bilateral ptosis resolved quickly after endoscopic third ventriculostomy (ETV).

Congenital muscular dystrophies in China.

Congenital muscular dystrophies (CMDs) are clinically and genetically heterogeneous conditions. We launched a nationwide study to determine the frequency of CMD in the Chinese population and assess the status of diagnosis and disease management for CMD in China. Cases were chosen from databases in 34 tertiary academic hospitals from 29 first-level administrative divisions (provinces, municipalities, autonomous regions, and special administrative regions), and medical records were reviewed to confirm the diagnoses. The study included 409 patients, of those patients who consented to genetic testing (n = 340), mutations were identified in 286 of them. The most common forms identified were LAMA2-related CMD (36.4%), followed by COL6-related CMD (23.2%) and α-dystroglycanopathy (21.0%). The forms of CMD related to mutations in LMNA and SEPN1 were less frequent (12.5% and 2.4%, respectively). We also recorded a significant difference in the diagnostic capabilities and disease management of CMD, with this being relatively backward in research centers from less developed regions. We provide, for the first time, comprehensive epidemiologic information of CMD in a large cohort of Chinese people. To our knowledge, this is the largest sample size of its kind so far highlighting the prevalence of CMD in China.