Allgrove syndrome with features of familial dysautonomia: a novel mutation in the AAAS gene

Allgrove syndrome (or triple-A syndrome) is a rare autosomal recessive disorder characterized by alacrima, achalasia, adrenal insufficiency (glucocorticoid in the majority of cases) and autonomic/neurological abnormalities. This disease is now known to be caused by mutation in the AAAS gene located on chromosome 12q13. Diagnosis should be readily available when the full-blown features are there, but it becomes less apparent when presentation is atypical or in the evolving process. We present a brother and sister (12 and 19 y old, respectively) born to consanguineous parents of Palestinian origin with Allgrove syndrome. The index patient was erroneously diagnosed to be a case of familial dysautonomia before the diagnosis of adrenal insufficiency was made at the age of 7.5 y, while his elder sister had only alacrima from birth and developed achalasia at the age of 15 y. She started to develop early evidence of adrenal disease at the age of 19 y. Both of them had neuroautonomic dysfunction. The diagnosis of Allgrove syndrome was confirmed in these two patients by studying the gene mutation in the family. The sequencing of the AAAS gene in the two patients identified a novel homozygous mutation within intron 5 (IVS5+1G-->A). Both parents as well as all three other children were heterozygous for the same mutation. CONCLUSION: These two cases illustrate the heterogenous nature and the intrafamilial phenotypic variability of Allgrove syndrome.     

Identification of two novel BCKDHA mutations in a Chinese patient with maple syrup urine disease

Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder affecting branched-chain amino acids. Mutations in the BCKDHA, BCKDHB, and DBT gene impair the branched-chain alpha-ketoacid dehydrogenase (BCKD) complex, resulting in the accumulation of branched-chain amino acids and branched-chain alpha-ketoacid in tissues and plasma. This leads to mental and physical retardation, feeding problems, and a maple syrup odor in the urine. In this study, we describe the clinical and biochemical manifestations of a sporadic mutation in a neonate with classic MSUD. Analysis of the BCKDHA gene revealed a compound heterozygous mutation consisting of two novel missense mutations (p.L103P and p.R265P). Viewing the protein with PyMOL indicated that the p.L103P and p.R265P mutations were, respectively, located in the helical region and core domains of the BCKD's Ela component. The p.L103P mutation affected the hydrophobic cores and is predicted to shorten the helix; the p.R265P mutation can predictably affect the cofactor binding site by ligating the associated manganese ion. In conclusion, we identified two novel missense mutations in the BCKDHA gene in a Chinese patient with MSUD.     

导致 Leigh综合征的 SURF1基因的两个新突变

目的 研究1例因常染色体SURFl基因新突变所致Leigh综合征患者的临床及遗传学的特点。方法 提取患儿外周血白细胞DNA,先进行线粒体基因热点突变的筛查,然后运用聚合酶链式反应扩增SURFl基因的全部外显子序列,进行正反向序列测定以检测突变。103名无关健康个体为正常对照组。结果 患儿从1岁2个月起出现进行性运动智力倒退,无力,喂养困难,2岁3个月时死于呼吸衰竭。其兄临床经过类似,2岁时死亡。线粒体基因筛查排除8993C〉T、3243A〉G、8344A〉G突变。SURFl基因序列测定显示该患者存在复合杂合性缺失,分别为外显子7第622位缺失A（622delA）和第653～654位缺失CT（653－654delCT）。结论　SURF1基因参与调控细胞色素C氧化酶复合物的组装,而细胞色素C氧化酶复合物缺陷是导致Leigh综合征的主要原因。本研究发现了SURFl基因622delA以及653-654delCT两个杂合性缺失为2个新突变,明确了患者的病因,并进一步充实了人类Leigh综合征致病基因库,将有助于今后Leigh综合征家系的遗传咨询。     

婴儿型神经元蜡样质脂褐素沉积病棕榈酰蛋白硫酯酶1基因的二个新突变

目的 报告在2例婴儿型神经元蜡样质脂褐素沉积病中发现棕榈酰蛋白硫酯酶1（PPT1）基因2个新的突变。方法 先证者1和2均在1岁以内出现进行性智能和运动发育倒退。病理检查诊断为婴儿型神经元蜡样质脂褐素沉积病。对先证者1和2以及前者的父母的PPT1基因编码区9个外显子及两旁的内含子序列设计引物进行PCR扩增,扩增产物测序检查。结果 先证者1存在复合杂合突变,分别为第6外显子的c550G→A即E184K点突变和第1内含子的IVS1＋1G→A剪接突变。其父亲在第1内含子也存在IVS1＋1G→A杂合性剪接突变,其母存在E184K杂合性突变。先证者2存在纯合突变,在第3外显子出现c272A→C即Q91P突变。对50例正常人DNA进行突变筛查均未发现相同突变。结论PPT1基因在第1内含子的IVS1＋1G→A剪接突变以及第3外显子的Q91P突变为2个以前没有报道的新突变,导致婴儿型神经元蜡样质脂褐素沉积病的发生。因此中国人的婴儿型神经元蜡样质脂褐素沉积病在PPT1基因的突变类型方面和其他地区的病例可能不完全相同。     

Phenotypic heterogeneity in AAAS gene mutation

We report the cases of two sibs of North African origin with AAAS gene mutation characterized by the heterogeneity of their phenotype. While an 8-y-old boy presented with acute adrenal insufficiency and mental retardation, the diagnosis was suggested by the clinical history of his 6-y-old sister who had symptomatic achalasia and chronic adrenal failure. Conclusion: Our observations corroborate the phenotypic heterogeneity reported in triple A syndrome, and underline the possibility of a variable intra-familial expression.     

A Chinese patient with acquired partial lipodystrophy caused by a novel mutation with LMNB2 gene

Acquired partial lipodystrophy (APL) is a rare disorder, mainly characterized by progressive loss of subcutaneous fatty tissue, starting from the face and spreading to the upper part of the body. The etiology of APL is unknown. It may be caused by mutations in the lamin B 2 (LMNB2) gene on 19p13.3. We present a Chinese patient who hadAPL for 12 years, which initially affected her face. She also suffered from marked fatty liver and a mild metabolic disorder. We identified a heterozygous T to C transition in exon 5 of the LMNB2 gene (c.694T>C), and, consequently, tyrosine for histidine (p.Y232H). However, these features and the mutation were absent in her parents. The p.Y232H has not been described previously. We provide clinical data to the genotype-phenotype discussion and further expanded the number of LMNB2 mutations.     

Two cases of Fanconi-Bickel syndrome: first report from China with novel mutations of SLC2A2 gene

Fanconi-Bickel syndrome (FBS) is a rare inherited disease caused by mutations in the glucose transporter 2 gene, SLC2A2. We reported the first two Chinese cases of FBS. Both cases presented typical clinical features of hepatomegaly, hypophosphatemic rickets, severely stunted growth, fasting hypoglycemia along with postprandial hyperglycemia, and proximal renal tubular dysfunction with disproportionately severe glucosuria. Genetic analysis of SLC2A2 gene revealed novel compound heterozygous mutations in both patients. The characteristics of being born as small for gestational age and apparent liver dysfunction in our cases have been seldom discussed in the literature. It seems FBS patients in general have lower birth weight than normal, but further data collection is still needed. Symptomatic treatments were effective, but the serum transaminase of patient 2 remained moderately increased, and he patient needed further follow-up. The present study will supplement the up-to-date clinical characteristic spectrum for FBS.     

新生儿枫糖尿病一例及其基因突变分析

目的 分析1例汉族经典型枫糖尿病新生儿的临床特点及其相关基因的致病性突变.方法 患儿男,生后8d因喂养困难于2013年4月转来上海交通大学附属儿童医院,收集患儿的临床资料及影像学检查等明确诊断后,提取患儿及其父母的外周血白细胞DNA检测BCKDHA、BCKDHB、DBT和DLD基因,确定患儿的基因突变位点,并进行生物信息学分析.结果 患儿表现为生后喂养困难、抽搐、代谢性酸中毒、尿有枫糖味等,CT示广泛脑白质低密度改变,串联质谱及尿气相色谱-质谱均符合枫糖尿病的诊断.基因测序结果在BCKDHB基因上发现2个错义突变:c.580 C＞T(p.Leu194Phe)和c.597 T＞G(p.Ser199Arg),均为杂合子,且为国际上未报道过的新突变.经Sanger测序发现其父亲携带了错义突变p.Leu194Phe,其母亲携带了错义突变p.Ser199Arg,符合家系共分离规律.PolyPhen蛋白功能预测发现此2个错义突变为有害的,很可能影响其蛋白功能.结论 BCKDHB基因c.580 C ＞T(p.Leu194Phe)和c.597 T＞G(p.Ser199Arg)复合杂合突变是该患儿的致病性突变,是该枫糖尿病患儿临床表现的基因分子基础,且为国际上未报道过的新突变.     

Three novel PHEX gene mutations in Japanese patients with X-linked hypophosphatemic rickets

X-linked hypophosphatemic rickets (XLH) is an X-linked dominant disorder characterized by renal phosphate wasting, abnormal vitamin D metabolism, and defects of bone mineralization. The phosphate-regulating gene on the X-chromosome (PHEX) that is defective in XLH has been cloned, and its location identified at Xp22.1. It has been recognized to be homologous to certain endopeptidases. So far, a variety of PHEX mutations have been identified mainly in European and North American patients with XLH. To analyze the molecular basis of four unrelated Japanese families with XLH, we determined the nucleotide sequence of the PHEX gene of affected members. We detected a new nonsense mutation (R198X) in exon 5, a new 3 nucleotides insertion mutation in exon 12 and a new missense mutation (L160R) in exon 5 as well as a previously reported nonsense mutation in exon 8 (R291X). These results suggest that: 1) PHEX gene mutations are responsible for XLH in Japanese patients, and 2) PHEX gene mutations are heterogeneous in the Japanese population similarly to other ethnic populations.     

Six novel mutations of the fibrillin-1 gene in Korean patients with Marfan syndrome

BACKGROUND: Mutations in the FBN1 gene, encoding fibrillin-1, result in Marfan syndrome (MFS). According to previous reports, the mutations in FBN1 share certain characteristics in each family with variable penetrance and overlapping symptoms, even in the same genotype. In the present study, we report six novel mutations and evaluate the clinical significance of these nucleotide changes. METHODS: To screen for nucleotide changes in all 65 exons of the FBN1 gene in 38 unrelated Korean patients, we performed polymerase chain reaction, single-strand conformational polymorphism (SSCP) and sequencing for the shift of the band in SSCP. RESULTS: We identified six mutations: a 2253 del 7 b.p., N1043S, C1254S, L1421F, C1895R and S2662P. CONCLUSIONS: These results suggest that many different mutations are responsible for MFS in the Korean population.     

两种新型Wiskott-Aldrich综合征蛋白基因突变的鉴定

目的 明确3例Wiskott-Aldrich综合征(WAS)患儿WAS蛋白(WASP)基因突变的类型。方法 根据典型临床表现(血小板减少、湿疹、反复感染),及淋巴细胞和血小板扫描电镜改变,采用PCR直接测序法,对3例疑为WAS的患儿及其母亲的WASP基因进行序列分析。结果 以正义、反义引物扩增的PCR产物分别测序,发现两种新型WASP基因突变：2例WAS孪生兄弟WASP基因第10外显子,第984位核苷酸C缺失突变(984delC),导致317位密码子后移码突变,于444位密码子提前出现终止密码(H317fsX444);其母亲为此突变WASP基因携带者。另l例WAS患儿WASP基因第ll外显子,第1388位核苷酸由G替换为T(1388G→T),为无义突变,使第452位密码子提前变为终止密码(E452X)。其母亲无此突变WASP基因。结论 鉴定出两种新型WASP基因突变,WASP基因序列分析对于不典型和散发WAS的诊断及WASP突变基因携带者的检出有重要作用。     

甲基丙二酸血症伴同型半胱氨酸血症患儿基因突变分析

目的 检测甲基丙二酸血症伴同型半胱氨酸血症患儿的MMACHC基因突变类型及突变频率.方法 依据串联质谱检测血中的酰基肉碱、气相色谱-质谱检测尿甲基丙二酸、血清同型半胱氨酸测定及维生素B12负荷试验等,对28例甲基丙二酸血症伴同型半胱氨酸血症患儿进行诊断;应用聚合酶链反应(PCR)对这些患儿及其部分直系亲属、健康对照组的MMACHC基因外显子进行扩增,通过DNA直接测序进行基因突变分析.结果 在28例患儿中27例检测到突变,共10种,其中2例仪检测到1个杂合突变,3例仅检测到多态性.突变集中在外显子3和4上(91.3%),以609G>A(W203X)最常见,突变频率为53.6%,其中10例为纯合突变,10例为杂合突变,其次为658_660delAAG(K220del),突变频率为8.9%,均为杂合突变.另外检测到6种未报道突变,分别为1A>G、365A>T、658_del660AAG、301-3_327del 30、567_568insT和625_626insT.3种基因多态性分别为-302T>G(rs3748643)、-234A>G(rs3728644)和321G>A(rs2275276).结论 揭示了中国甲基丙二酸血症伴同型半胱氨酸血症患儿的部分基因突变谱,其中609G>A(W203X)可能为热点突变.     

儿童肾母细胞瘤WT1基因突变四例报道

目的 研究儿童肾母细胞瘤患者WT1基因的突变类型及突变频率.方法应用聚合酶链反应(PCR)扩增出54例儿童肾母细胞瘤患者WT1基因全部10个外显子及其相邻内含子序列,经纯化后进行PCR产物直接测序.结果 4例患者WT1基因分别存在3个杂合无义突变及1个纯合错义突变.例1患者WT1基因7号外显子第1006位碱基A→T杂合突变,造成第336号氨基酸由赖氨酸转变为终止密码子,即K336X.例2患者WT1基因9号外显子第1168位碱基c→T杂合突变,造成第390号氨基酸由精氨酸转变为终止密码子,即R390X.例3患者WT1基因6号外显子第814位碱基G→T杂合突变,造成第272号氨基酸由谷氨酸转变为终止密码子,即E272X.例4患者WT1基因10号外显子第1228位碱基A→G纯合突变,造成第410号氨基酸由丝氨酸转变为甘氨酸,即S410G.结论 散发的中国儿童肾母细胞瘤患者WT1基因外显子突变的发生率与国外报道相近,检测到的4例突变患者中3例为无义突变、1例为错义突变.     

Laron综合征家系患者生长激素受体基因突变分析

目的研究Laron综合征患者的临床特点及生长激素受体（GHR）的基因突变。方法对一家系中2例表现为身材明显落后的患儿进行研究，分别进行体格测量和GH-IGF—I轴功能测定。提取外周血白细胞基因组DNA，运用聚合酶链式反应（PCR）扩增GHR基因第2～9外显子及其两侧的侧翼序列，直接进行测序，将所测结果与正常人GHR基因序列进行对比，确定突变位点和突变类型。对突变基因均经2次测定证实。结果2例患儿自出生后身长明显落后于同龄儿童，呈现Laron综合征的独特面貌，空腹血清GH值均明显高于正常儿童。空腹血清IGF-I明显低于同年龄同性别正常儿童。血浆IGFBP-3和GHBP低于检测线。GHR基因序列测定结果显示2例患儿均存在外显子4上第65为氨基酸的纯合突变S65H，为新发现突变。结论Laron综合征患者存在典型的面貌特征，结合血GH、IGF-I、IGFBP-3和GHBP测定可以明确诊断。GHR基因外显子4上S65H突变可能是该Laron综合征患者的致病原因。     

儿童Lowe综合征OCRL基因突变2例报告

目的探讨儿童Lowe综合征的临床特点和基因特征。方法分析2例Lowe综合征患儿的临床资料和OCRL基因检测结果,并复习相关文献。结果 2例患儿均为男性,均存在小分子蛋白尿、高钙尿症、佝偻病和肾结石。例2患儿还有轻度代谢性酸中毒、糖尿和隐睾症。例1患儿生后不久发现有视力异常和先天性白内障,并行手术治疗,同时存在精神运动发育落后,头颅磁共振成像(MRI)示胼胝体发育不良。例2患儿就诊时肾外症状不明显,但眼科检查发现有先天性白内障,头颅MRI示脑发育低下、脑白质髓鞘化延迟,且随访过程中逐渐出现智力发育落后。OCRL基因检测发现2个突变,例1为剪切位点突变NG 008638.1:g.46846-46848del TAA/ins C,例2为缺失移码突变NM000276.3:c.321del C,两种突变以前文献均未报道。结论 Lowe综合征的诊断主要通过临床表现和OCRL基因检测,对于有先天性白内障、肾小管病变的患儿需要与Lowe综合征鉴别。本研究发现2个OCRL基因的新突变。     

Wolcott-Rallison综合征一例报告及其EIF2AK3基因突变检测

目的 报道一例Wolcott-Rallison综合征患儿,研究患儿真核生物翻译起始因子-2α-激酶-3基因(eukaryoticinitiation factor 2α kinase 3,EIF2AK3)的突变情况,为该病的临床诊断、基因诊断与遗传咨询提供依据.方法 分析患儿的临床症状、体征、生化检查及骨骼X线检查并做出临床诊断;提取患儿及其父母的基因组DNA,针对EIF2AK3基因设计特异性引物,应用降落聚合酶链式反应(Touch-down PCR)扩增基因的全部外显子及外显子-内含子交界区,对扩增产物进行直接测序分析.结果 (1)9岁4个月男性患儿,身高108 cm,智力相当于6岁儿童发育水平;出生3个月时被诊断为1型糖尿病,正规胰岛素治疗后空腹血糖常高于11.0 mmol/L,最高达23.5 mmol/L;面容异常;肝脏于肋下5 cm,剑突下2 cm;骨骼畸形,X线提示多发性骨骺发育不良.(2)患儿EIF2AK3基因的外显子8中检测到c.1408_1409insT(p.S470FfsX7)杂合突变,外显子9中检测到c.1596T＞A(p.C532X)杂合突变,2个突变位点分别在患儿母亲和父亲的基因中得到验证.结论 Wolcott-Rallison综合征临床特点:新生儿或婴儿早期发生的1型糖尿病,多发性骨骺发育不良,体格和智力发育迟缓,多系统损伤;结合患者临床表现与生化、物理检查,对致病基因EIF2AK3进行突变检测是诊断Wolcott-Rallison 综合征的可靠方法.EIF2AK3基因c.1408_1409insT与c.1596T＞A是导致该患儿出现Wolcott-Rallison综合征表型的致病突变,患儿为EIF2AK3基因突变的遗传复合体,这2个突变在国内外均未见报道,属新突变.

Abstract：

Objective Wolcott-Rallison syndrome(WRS)is a rare autosomal recessive disorder characterized by the association of permanent neonatal or early-infancy insulin-dependent diabetes,multiple epiphyseal dysplasia and growth retardation,and other variable multisystem clinical manifestations.Here we describe a Chinese boy affected by WRS.Genetic testing of his EIF2AK3 gene was performed in order to elucidate molecular variations and subsequently to provide credible genetic counseling for prenatal diagnosis in his family. Method Based on analysis of a nine-year-old boy's clinical symptoms associated with biochemical examination and imaging,the diagnosis of WRS was therefore made.Genomic DNAs were extracted from peripheral blood leukocytes from the boy and his parents with their informed consent for genetic studies.All EIF2AK3 exons and intron-exon boundaries were amplified by Touch-down polymerase chain reaction(Touch-down PCR)and sequenced.Result Direct sequencing of PCR products revealed the presence of a heterozygous T insertion(c.1408_1409insT)in exon 8 of the EIF2AK3 gene leading to frameshifting and termination,and another heterozygous T to A exchange(c.1596T ＞ A)in exon 9 of the EIF2AK3 gene resulting in nonsense C532X mutation. Conclusion Combining mutation screening of EIF2AK3 gene with clinical manifestations and effective examination may provide a reliable diagnostic method for patients.In this research,two novel mutations identified in the Chinese boy locate in the catalytic domain of the EIF2AK3 gene,disrupting the ability of autophosphorylation,leading to the truncated proteins that are unable to phosphorylate the natural substrate,which are responsible for the phenotype of Wolcott-Rallison syndrome.