Congenital muscular dystrophy caused by beta1,3-N-acetylgalactosaminyltransferase 2 gene mutation: Two case reports

INTRODUCTION

Congenital muscular dystrophy (CMD) refers to the primary and progressive myopathy that occurs at birth or within a few months after birth, usually causing considerable burden to the child and their families and society. The main clinical manifestations of CMD include premature myasthenia, hypodystonia, motor development retardation, and joint contracture with or without central nervous system involvement. The creatinase level tends to increase to varying degrees, myogenic damage can be seen on electromyography, and muscular dystrophy is the most common muscle pathology. Ge[1] reported that the prevalence rate of CMD in China was 0.017-0.083/100000. CMD is a group of hereditary diseases with strong heterogeneity caused by anti-dystroglycan (DG) deficiency. DG is a protein that is widely expressed in a variety of tissues, including the brain, Schwann cells of peripheral nerves, neuromuscular junction, muscle, liver, lung, and skin[2]. DG is cleaved into α-DG and β-DG after translation. The core structure of α-DG is dumbbellshaped, with a spherical C-terminal and an N-terminal at the two ends, respectively,while the middle is connected by a mucoprotein-like structure. α-DG undergoeslinked glycosylation, which rarely occurs[3]and then forms an antidystrophin-glycoprotein complex with β-DG. Then, it binds with ligands containing a laminin globular domain in the extracellular matrix, such as laminin, perlecan,agglutinin, axon protein, and pikacurin, to maintain muscle cell integrity[4], thus playing an important role in brain development[5]. α-DG has many glycosylation sites,short glycoprotein fragments, complex functions, and diverse pathogenic genes[6].Once the glycosylation of α-DG is impaired, it can trigger many pathophysiological processes, such as cell migration disorder[7] or α-dystroglycanopathy (α-DGP)[8].Recent studies[9] have shown that the gene located in 1q42.3 containing 64292 base pairs is one of its pathogenic genes, which encode beta1,3--acetylgalactosaminyltransferase2 (B3GALNT2). The deficiency of this enzyme can lead to the damage of α-DG glycosylation, consequently impairing the function of α-DG and affecting cell proliferation, migration, differentiation, and maintenance of tissue integrity, resulting in α-DGP[10]. Its pathogenic type was autosomal recessive inheritance.

互聯(lián)網(wǎng)是以連接為目的導向的社會網(wǎng)絡和復雜網(wǎng)絡，互聯(lián)網(wǎng)內(nèi)容傳播的本質其實是跨越平臺建立人與人之間的連接。一切的交互都在產(chǎn)生連接行為，連接既是網(wǎng)絡演化的手段也是網(wǎng)絡演化的目標。內(nèi)容創(chuàng)作的目標不再僅僅是獲得用戶的單次閱讀，而是獲得用戶持續(xù)性的互動和穩(wěn)定的認知連接。有了連接，才有用戶和粉絲，社交分享量甚至比單次閱讀量更加重要。沒有一種連接是不可被替代的，替代的原則是連接得更強、更快、更緊、更美。[3]所有連接一旦建立，將不再滿足于單一的連接形態(tài)，隨著時間推移，它會不斷疊加更為新鮮更為緊密的連接形態(tài)，從而形成連接的質變。

CASE PRESENTATION

Chief complaints

Case 2: Genetic examination showed that thecarried a compound heterozygous mutation (Figure 2). The mutation sites on the allele included c.261-2A>G(splicing) from the mother (Figures 2A and 2B) and c.979G>A (p.D327N) from the father (Figures 2C and 2D). The former was a missense mutation, and the latter was a nonsense mutation, which led to protein truncation.

Case 2: A 45-mo-old Chinese Han boy presented with delayed growth and development from childhood and an abnormal scalp in June 2019.

雙饋風機等效慣性時間常數(shù)計算及轉差率反饋慣量控制策略//劉皓明,任秋業(yè),張占奎,李琰,許波峰//(17):49

History of present illness

Case 1: The child showed signs of developmental delay since childhood. He could raise his head at 5 mo, sit at 8 mo, walk alone at 1 year and 8 mo, and say the Chinese words for “mother” and “father” at 28 mo.

2009年到2010年，筆者在香港和上海兩地，對香港跨界華人企業(yè)家在中國大陸的發(fā)展進行了人類學田野研究。以下兩個人類學案例一步表明香港跨界華人企業(yè)家如何立足專業(yè)網(wǎng)絡和互信關系，憑借跨界溝通能力和中國的政策制定者取得共識。從而確保成功的香港經(jīng)驗和商業(yè)模式能夠在中國大陸社會主義市場經(jīng)濟的土壤中取得生存和發(fā)展。

History of past illness

Case 1: The patient had no special past history.

隨著經(jīng)濟發(fā)展，中國對能源的需求高速增長，受國內(nèi)資源條件的限制，未來中國原油在很大程度上將依賴進口。據(jù)中國海關進口原油來源地數(shù)據(jù)統(tǒng)計，目前中國原油進口區(qū)域中，中東、非洲、南美洲及俄羅斯位居前列，俄羅斯目前主要是管道和鐵路運輸，成本較高，其他國家和主要原油運輸航線有著政治和海盜的風險，對中國能源安全造成威脅，如中東、馬六甲海峽等。因此，從北極地區(qū)進口原油，建立多元化格局，保證原油充足供應是我國長期的戰(zhàn)略選擇。

（3）指事字的教學。漢字的演變是由形象逐漸向抽象發(fā)展的過程，教師在教授學生指事字時也應注意給學生提供有關漢字的來源，如在教“朱”字時，可告訴學生，“朱”字在的一橫在木字之中，指的是木的中間，也就是樹的中間，而這棵樹剛好是松柏樹，樹中是赤紅色的，所以朱字也就有紅色的含義了。

稅收執(zhí)法部門有一定的裁定權，稅收籌劃能否真正地得到實施，還需要考慮當?shù)囟愂詹块T的意見。因此，稅收籌劃人員在做稅收籌劃的過程中，應當加強與稅務部門的交流，及時獲取有用的稅收信息，加強對征管的具體要求和限制的了解，可以降低稅收籌劃的違規(guī)風險。

Case 2: Meningocele was seen in the parietal and occipital region after birth, which then gradually healed.

Personal and family history

Case 1: The child was the fifth fetus and the second delivered by cesarean section at 38 wk of pregnancy. There was no significant family history.

Case 2: The child was the second fetus and delivered by full-term natural delivery.There was no significant family history.

Physical examination

Case 1: Physical examination revealed that the child could understand and respond to instructions, walked with “duck step”, and had no skin abnormalities or abnormal palpebral fissures. The bilateral pupils were round, equal in size, and sensitive to light reflex. The patient had no stiff neck, and no obvious heart, lung, and abdomen abnormalities. He had normal muscle strength of the extremities, bilateral biceps reflex, knee-tendon reflex, and active Achilles tendon reflex. He had low muscle tone and positive bilateral Babinski signs.

Case 2: The child could raise his head at 6 mo, sit alone at 12 mo, and walk at 24 mo.At the time of this visit, he still walked with a spastic gait. At present, he could pronounce a small number of disyllabic words such as the Chinese words for “father”and “mother”.

Case 2: Physical examination revealed that the child could understand and respond to instructions well, and walked with a spastic gait. An abnormal area of approximately 3 cm × 2 cm was visible in the parietal occipital area of the scalp; it was blue and purple in color, lacked hair growth, and showed no rupture, no tenderness, and no fluctuation. The bilateral eye fissure had no deformity, and bilateral pupils were round, equal in size, and sensitive to light reflex. There were no limitations of eye movement; no stiff neck; and no obvious abnormalities in the heart, lung, and abdomen. The muscle strength of the extremities was normal, and muscle tension was high. Bilateral biceps reflex, knee-tendon reflex, and Achilles tendon reflex were active,and bilateral Babinski signs were negative.

Laboratory examinations

Case 1: The leukoencephalopathy gene package (McKinnon) was used for sequencing,and the results demonstrated that thegene had a compound heterozygous mutation (Figure 1), and the allele mutations included c.1068dupT (p.D357_D358 delinsX) from the father (Figures 1A and 1B) and c.40G>C (p.G14R) from the mother(Figures 1C and 1D). The former was a nonsense mutation, which led to protein truncation, and the latter was a missense mutation.

At present, there are few reports about thegene causing CMD, and the relationship between genotype and phenotype is still not fully understood. In this paper, the pathogenic characteristics of this gene in two cases of α-DGP caused bygene mutation found in our hospital are summarized and discussed in view of previous reports.

Case 1: A 49-mo-old Chinese Han boy presented with abnormal walking posture in January 2019.

Imaging examinations

Case 1: At the age of 2 years and 4 mo, electromyography of the extremities was generally normal. Visual evoked potentials (Figure 3A) showed that both eyes were stimulated, each wave was well-differentiated, and P1 latency was significantly prolonged. Somatosensory evoked potentials (Figure 3B) showed that both upper limbs were stimulated, the cortical and surrounding waves were well-differentiated,and the latencies were roughly normal. Auditory evoked potentials (Figure 3C)suggested that bilateral ears were stimulated, the waveform of the left side was relatively poor, the latencies of the right III, IV, and V waves were prolonged. Head magnetic resonance imaging (MRI) showed cerebellar cortical cysts (Figure 4A),multiple flaky and linear equal/slightly long T1, long T2, and high fluid-attenuated inversion recovery signals around the bilateral ventricles of the brain (Figures 4B and 4C).

The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).

制定智能化建筑用電節(jié)能設計時，一定要整體把握用電設施的布局分配、負荷容量及功率大小等信息，以此為基礎，選擇恰當、合理的節(jié)能供配電設備，保證用電設備正常工作的同時，最大限度地降低能耗的損失。

FINAL DIAGNOSIS

gene can be used as one of the candidate genes for screening CMD,cognitive development retardation, epilepsy, and multiple brain developmental malformations in infants.

TREATMENT

Both cases received coenzyme Q10 and levocarnitine. The giant arachnoid cyst in case 2 was resected.

OUTCOME AND FOLLOW-UP

Case 1

The patient could pronounce 2- to 3-syllable words, and his walking posture was improved over the course of the follow-up.

Case 2

At the latest follow-up visit, the child’s walking posture was improved compared to before, although language development did not significantly improve. He recovered well after resection of the giant arachnoid cyst, and the meningocele gradually selfhealed.

A total of 21 articles were found using the search key word ”” on the PubMed website, of which five articles were related to human CMD. The first article was published in 2013. The five articles included four pedigrees and seven sporadic patients. A total of 21 patients were reported, including the two patients in the present case report. Tables 1 and 2 present a summary of all these cases: (1) The nervous system was involved in all cases, and cognitive and motor developmental disorders were the most commonly encountered clinical symptoms (100%), followed by seizures(52.6%) and low muscle tension (64.3%); (2) Abnormal head MRI may be manifested as periventricular white matter lesion (81.3%), neuronal migration disorder (68.8%),brainstem and/or cerebellar dysplasia (56.3%), cerebellar cortical cyst (50%), and severe hydrocephalus (31.25%); (3) Muscle involvement was seen in 63.2% of patients,and the increased creatinase level ranged from 300 to 1740 U/L, which was even higher in patients with a more severe condition; and (4) Eye involvement occurred in 28.6% of the cases. The common symptoms were optic nerve atrophy and eye fissure deformities. In severe cases, glaucoma, cataract, and even blindness could be observed.

DISCUSSION

This study reports two cases of CMD caused bygene mutation. Both cases had an abnormal gait and significant delays in language development. Head MRI was performed for both children and revealed the presence of white matter lesions in the brain. The present report suggested that the cognitive language retardation and white matter lesions in CMD were caused bygene mutation. New symptoms of meningocele and giant arachnoid cyst were also encountered in one of our cases. To our knowledge, this is the first study to use electrophysiological examination of the audiovisual conduction pathway in children with this type of gene mutation. The findings suggest that even if audiovisual function was normal, the evoked audiovisual potential should be examined to investigate for potential abnormalities. The white matter lesions in case 2 were gradually absorbed and improved with age. He recovered well after surgical resection of the giant arachnoid cyst, and the meningocele gradually self-healed. These results suggested that some of the symptoms associated with the gene mutation might have a tendency to self-heal, which was consistent with the report of Hedberg[11]. Further studies are required to determine whether this is related to the peak age of gene expression. Both of the present cases had compound heterozygous mutations, the gene mutation sites were from their parents, and the mutations were compatible with autosomal recessive inheritance.

Case 1 had two compound heterozygous mutations in thegene; one of them was c.1068dupT (p.D357_D358delinsX), which was a nonsense (zero-effect)mutation that may lead to loss of gene function. The frequency in the normal population database was 0.00010, indicating that this was a low-frequency variation(PM2). The bioinformatics protein function prediction software packages SIFT,PolyPhen_2, and REVEL all predicted it as unknown. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, the variation was preliminarily determined as a suspected pathogenic variation. The other was c.40G>C(p.G14R), which was a missense mutation. It was (-) in the normal population database, which indicated a low-frequency variation (PM2). It existedwith another pathogenic variation (PM3). SIFT, PolyPhen_2, and REVEL predicted it as harmful, harmful, and benign, respectively. According to the ACMG guidelines, the variation was preliminarily determined as being of unknown clinical significance. In case 2, there were two compound heterozygous mutations in thegene:One was c.261-2A>G, which was located in the classical splicing site (± 1, 2). It was likely to affect the normal splicing of mRNA and lead to protein truncation. The frequency in the normal population database was 0.00004, which showed that this was a low-frequency variation (PM2). According to the ACMG guidelines, this variation was preliminarily determined to be a suspected pathogenic variation (PS1). The other site was c.979G>A (p.D327N), which was a known PS1 in the Human Gene Mutation Database, and the frequency of variation in the normal population was 0.00003 (PM2).In the transposition, the suspected pathogenicity variation c.261-2A>G (PM3) was detected. SIFT, PolyPhen2, and Mutation Taster all predicted that the mutation was harmful (PP3). According to the ACMG guidelines, the variation was preliminarily determined to be a suspected PS1. According to the clinical symptoms and gene results, both children were diagnosed as having CMD caused by thegene mutation. Each child had one missense mutation, and each had a mutation leading to protein truncation. Case 1 had a frameshift mutation leading to protein truncation,whereas case 2 had a splicing mutation leading to protein truncation, suggesting that truncation mutation may be related to a severe clinical phenotype.

In this study, data from two hospitalized patients and data of 19 patients obtained from a search of the previous literature were collected, yielding data from a total of 21 patients with α-DGP caused bygene mutation. Clinical manifestations included common symptoms such as nervous system, muscular dystrophy, eye development malformation, and rare symptoms such as sensorineural deafness.Moreover, 100% of the 21 patients had nervous system involvement, and delayed cognitive and motor development. In severe cases, patients had no cognitive and motor development, and most cognitive disorders included language retardation.Patients with a mild lesion on MRI only had periventricular white matter lesions,while patients with severe lesions seen on MRI had brainstem and/or cerebellar dysplasia and neuronal migration disorders. Among the 21 patients, 63.2% had elevated creatinase that was mostly between 300 and 1740 U/L, and 26.6% of the patients had eye involvement. The common symptoms were optic nerve atrophy and eye fissure deformities (excessive small or large). Patients with extensive nervous system and muscle involvement had severe ocular symptoms such as glaucoma,cataracts, and even blindness.

明月的關系更好，而且說起來還有些復雜，邊峰是自己妻子妹妹的同學。秦明月當年破獲幾起大案，后來都是警方的宣傳人員通過邊峰推向媒體的，邊峰還專門寫過他的專題報道，為其獲評省十佳警察起了很大的作用。他知道邊峰喊他是想干什么，干脆裝著沒聽見，皺眉返回大廳，命令對寄存處的東西進行一次清查。

首次實驗采用的方案是，對所有論文進行分詞，去除連詞、介詞、代詞等結構性詞匯，再將其余詞匯進行詞頻檢索，按詞匯出現(xiàn)頻次高低排序，分析高頻次詞匯的詞性規(guī)律。這是一般文本挖掘常用的方法，這樣得出的高頻詞匯表中，很多日常用詞居于排行前列，高頻專業(yè)詞匯數(shù)量太多且不集中，難以得出精煉的研究熱點，故放棄此實驗方案。

There were 12 pairs of alleles in 21 patients involving 15 Loci. Among them,c.979G>A (p.D327N) appeared three times, and c.822_823dup (pI276Lfs*26) appeared twice, suggesting that the above two sites may be focal mutations. It was further speculated that the severity of thegene mutation was still related to its mutation type and site. All four patients with biallelic truncated mutations in sporadic cases 2, 3, 7, and 19 had neuronal migration disorders (polymicrogyria or cobblestonelike surface with no gyri). Pedigree 1 and sporadic cases 8 and 21 had severe truncated mutations of a single allele (the sites were all before the 103amino acid), and they also had neuronal migration disorders or developmental brain malformations.Pedigree 3 and sporadic case 20 had mild truncated mutations of a single allele (the sites were all after the 276amino acid), and they had only white matter involvement.Other forms of mutation had relatively mild symptoms. The above results suggested that patients with a truncated mutation of the gene located more at the front of the mutation site had more severe symptoms. The missense mutation was often associated with relatively mild symptoms. Sporadic type 1 is special, in that it is a compound heterozygous missense mutation that is associated with severe symptoms such as polymicrogyria malformation and eye and muscle involvement. Further studies are required to study the mechanism underlying sporadic type 1 mutation.

CONCLUSION

This article reports two cases of CMD caused bygene mutation. Each case carried a truncated mutation and a missense mutation, while three of the four variants have not been previously reported; thus, our findings in this case report expand the gene database. Case 2 had two new phenotypes: Giant arachnoid cyst, which recovered well after surgical resection, and meningocele after birth, which gradually self-healed. These data broadened the phenotypic spectrum of the gene. Clinical characteristics of the gene mutation are summarized and analyzed through a literature search, providing clues for clinicians to diagnose and treat this gene mutation. Due to the limitation of a small number of patients, absence of functional verification, and lack of evidence at the cellular level, the clinical characteristics and pathogenic mechanisms of this mutation were not completely clarified. Further studies at a clinical level are required to support our findings.