A novel G6PD mutation leading to chronic hemolytic anemia

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an important cause of hemolytic anemia worldwide. Severely affected patients have chronic hemolysis with exacerbations following oxidative stress. Mutations causing severe chronic non-spherocytic hemolytic anemia (CNSHA) commonly cluster in Exon 10, a region important for protein dimerization. An African-American male presented at age 2 weeks with pallor and jaundice, and was found to have hemolytic anemia with G6PD deficiency. His severe clinical course was inconsistent with the expected G6PD A(-) variant. DNA sequencing revealed two common mutations (A(-)) and a third novel Exon 10 mutation. This inherited haplotype represents a novel triple G6PD coding mutation causing chronic hemolysis.     

丙酮酸激酶缺乏症2 家系基因变异分析

目的探讨丙酮酸激酶缺乏症(PKD)的临床及遗传学特点。方法回顾分析2例PKD患儿的临床资料,复习相关文献总结PKD的临床及遗传学特点。结果 2例患儿均为女孩,年龄3岁8个月和3岁10个月;均表现为巩膜黄染,中度贫血(血红蛋白60 g/L)。全外显子测序分析发现,例1的PKLR基因存在c.106GT以及c.817CT复合杂合突变,其中c.106GT突变遗传自父亲,而c.817CT遗传自母亲,患儿姑姑为c.106GT突变携带者;例2 PKLR基因存在c.1279GT以及IVS6-1GT复合杂合突变,其中c.1279GT突变遗传自母亲,IVS6-1GT突变遗传自父亲。例1的复合杂合突变未影响患者PKLR基因表达,而例2剪接位点IVS6-1GT突变可能影响PKLR基因的RNA水平。结论两个PKD家系均为PKLR基因变异,基因检测有助PKD诊断。     

Relative red blood cell enzyme levels as a clue to the diagnosis of pyruvate kinase deficiency

Evaluation of two patients with transfusion dependent anemia revealed RBC pyruvate kinase to be 33% and 41% of the mean normal value, with normal or high values of other RBC enzymes. Parental PK activities were just below normal in three of four of the parents. Subsequent DNA analysis revealed both patients to be compound heterozygotes for PKLR gene mutations, two of which are previously undescribed. Borderline low pyruvate kinase activities with increased in other RBC enzyme activities should prompt consideration of measurement of parental enzyme activities, and confirmation by DNA analysis if available.     

COL4A5 基因插入突变致Alport 综合征一家系报告

目的探讨Alport综合征的临床特点及其相关致病基因。方法回顾分析1个Alport综合征家系的临床资料。结果先证者,男,11岁8个月,COL4A5基因中鉴定出TTCT插入突变(c.41_42 dup TCTT),该插入突变引起了移码突变。使用Integrative Genomics Viewer软件进行分析,该移码突变导致自之后的第13个氨基酸残基发生改变,且在第40个氨基酸残基处出现终止密码子,导致蛋白表达提前终止。患儿母亲和外祖母均携带该变异,分别在35岁和34岁时达到终末期肾病,且都有听力受损,但未发现眼部异常。家系分析表明该变异与该家系患病成员存在共分离关联。结论基因检测有助于Alport综合征确诊,该家系扩展了Alport综合征的致病变异谱。     

Use of targeted next‐generation sequencing for molecular diagnosis of craniosynostosis: Identification of a novel de novo mutation of EFNB1

Craniofrontonasal syndrome (CFNS; MIM#304110) is characterized by asymmetric facial features with hypertelorism and a broad bifid nose due to synostosis of the coronal suture. CFNS shows a unique X‐linked inheritance pattern (most affected patients are female and obligate male carriers exhibit a mild manifestation or no typical features at all) associated with the ephrin‐B1 gene (EFNB1) located in the Xq13.1 region. In this study, we performed targeted, massively parallel sequencing using a next‐generation sequencer, and identified a novel EFNB1 mutation, c.270_271delCA, in a Japanese female patient with craniosynostosis. Because subsequent Sanger sequencing identified no mutation in either parent, this mutation was determined to be de novo in origin. After obtaining molecular diagnosis, a retrospective clinical evaluation confirmed the clinical diagnosis of CFNS in this patient. Comprehensive molecular diagnosis using a next‐generation sequencer would be beneficial for early diagnosis of the patients with undiagnosed craniosynostosis.     

Next‐generation sequencing for mitochondrial diseases: A wide diagnostic spectrum

Background: The current diagnostic approach for mitochondrial disorders requires invasive procedures such as muscle biopsy and multiple biochemical testing but the results are often inconclusive. Clinical sequencing tests are available only for a limited number of genes. Recently, massively parallel sequencing has become a powerful tool for testing genetically heterogeneous conditions such as mitochondrial disorders. Methods: Targeted next‐generation sequencing was performed on 26 patients with known or suspected mitochondrial disorders using in‐solution capture for the exons of 908 known and candidate nuclear genes and an Illumina genome analyzer. Results: None of the 18 patients with various abnormal respiratory chain complex (RCC) activities had molecular defects in either subunits or assembly factors of mitochondrial RCC enzymes except a reference control sample with known mutations in SURF1. Instead, several variants in known pathogenic genes including CPT2, POLG, PDSS1, UBE3A, SDHD, and a few potentially pathogenic variants in candidate genes such as MTO1 or SCL7A13 were identified. Conclusions: Sequencing only nuclear genes for RCC subunits and assembly factors may not provide the diagnostic answers for suspected patients with mitochondrial disorders. The present findings indicate that the diagnostic spectrum of mitochondrial disorders is much broader than previously thought, which could potentially lead to misdiagnosis and/or inappropriate treatment. Overall analytic sensitivity and precision appear acceptable for clinical testing. Despite the limitations in finding mutations in all patients, the present findings underscore the considerable clinical benefits of targeted next‐generation sequencing and serve as a prototype for extending the clinical evaluation in this clinically heterogeneous patient group.     

A case of inherited type 1 and type 2A von Willebrand disease confirmed by diagnostic exome sequencing

A 10‐year‐old male and his family members visited a pediatric hematology clinic due to coagulopathy. Laboratory tests indicated von Willebrand disease (vWD) in all the family members. We conducted diagnostic exome sequencing for confirmation. The patient was confirmed to be a compound heterozygote for vWD: c.2574C > G (p.Cys858Trp) from his father (known variant of vWD type 1) and c.3390C > T (p.Pro1127_Gly1180delinsArg) from his mother (variant known to result in exon 26 skipping in vWD type 2A). He was managed with factor VIII and von Willebrand factor complex concentrate during palatoplasty due to bleeding despite pre‐operative desmopressin injection. The operation was completed successfully.     

A novel G473A mutation in the glucose‐6‐phosphate dehydrogenase gene

Hereditary deficiency in human glucose‐6‐phosphate dehydrogenase (G6PD) is mostly caused by single nucleotide change in the G6PD gene which leads to single amino acid substitution. In 104 cases of Chinese children with G6PD deficiency, RT‐PCR‐DGGE (denaturing gradient gel electrophoresis) combined with DNA sequencing was carried out to screen the mutations within the coding region of G6PD gene. A novel missense mutation (G473A), predicting a Cys‐to‐Tyr substitution at codon 158, was identified in a male infant patient and confirmed in his mother. This G6PD variant (158 Tyr) showed decreased enzyme activity, belonging to WHO Class II. We designated this variant as G6PD Shenzhen by the birthplace of the propositus. Pediatr Blood Cancer. 2010;55:383–385. © 2010 Wiley–Liss, Inc.     

Whole exome sequencing identified a novel single base pair insertion mutation in the EYS gene in a six generation family with retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of inherited progressive retinal dystrophies (RD) and is characterized by photoreceptor degeneration. RP is clinically and genetically heterogeneous disorder. More than 70 genes are known and, thus, identification of causative genes and mutations in known genes is challenging. This study was designed to identify the underlying genetic defect in a large extended Saudi family with multiple RP affected members. Fundus photography, Optical Coherence Tomography (OCT) and visual field perimetry were performed for affected individuals. Whole exome sequencing was used to detect the underlying genetic defect in a large family with 12 affected individuals showing autosomal recessive isolated RP. WES data analysis identified a novel insertion mutation in the EYS (eyes shut homolog) gene (c.910_911insT; p.Trp304LeufsTer8). Sanger sequencing validates the variant discovered through exome in all 12 affected individuals and showed that this mutation is segregating with RP phenotype in an autosomal recessive manner in 51 individuals of the family tested here. Our study expands the mutation spectrum of EYS gene in RP patients and extends the body of evidence that supports the importance of EYS gene in eye development.     

Cord blood transplantation in a young child with pyruvate kinase deficiency

Unrelated cord blood transplantation (CBT) was performed for the treatment of pyruvate kinase (PK) deficiency in a female pediatric patient at the age of 1 year 7 months, who had been in severe and frequent transfusion‐dependent hemolytic anemia, despite red blood cell (RBC) PK activity 5.52 IU/gHb. pyruvate kinase‐liver and RBC (PK‐LR) had a compound heterozygous mutation located on exon 8: c.1044G > T/c.1076G > A (K348N/R359H). Hemoglobin and RBC PK corrected to 13.5 g/dL and 9.00 IU/gHb, respectively, with gene correction at 6 months after CBT. CBT should be considered as an option for useful treatment in children with severe PK deficiency in the absence of HLA identical sibling with normal RBC PK activity.     

Successful treatment of mixed‐type autoimmune hemolytic anemia with rituximab in a child following liver transplantation

Haller W, Hind J, Height S, Mitry R, Dhawan A. Successful treatment of mixed‐type autoimmune hemolytic anemia with rituximab in a child following liver transplantation.
Pediatr Transplantation 2010: 14: E20–E25. © 2009 John Wiley & Sons A/S. Abstract: Development of a severe form of mixed‐type AIHA after orthotopic liver transplantation is a rare, but a life‐threatening event. We report a case of mixed‐type AIHA that developed in a child after hepatocyte and living‐related orthotopic liver transplantation for factor VII deficiency.     

TRIM37基因新剪接位点突变致Mulibrey侏儒症1例报告

目的探讨Mulibrey侏儒症的临床及基因突变特点。方法回顾分析1例经基因检测确诊Mulibrey侏儒症患儿的临床资料、基因检测及家系验证结果。结果男性患儿,12岁5个月,有身材矮小、皮肤牛奶咖啡斑、三角形脸、牙齿不齐、肝肿大,合并缩窄性心包炎。二代测序检测分析发现患儿17号染色体TRIM37基因存在一个未报道的剪接区纯合变异位点IVS13-1GC,分别来自于父母;患儿同胞弟弟未检出该变异;参考ACMG遗传变异分类标准与指南,判定为致病性变异。结论发现1例TRIM37基因剪接位点突变导致的Mulibrey侏儒症,但尚需RNA或蛋白质功能分析确认。