Clear relationship between ETF/ETFDH genotype and phenotype in patients with multiple acyl-CoA dehydrogenation deficiency

Mutations in electron transfer flavoprotein (ETF) and its dehydrogenase (ETFDH) are the molecular basis of multiple acyl-CoA dehydrogenation deficiency (MADD), an autosomal recessively inherited and clinically heterogeneous disease that has been divided into three clinical forms: a neonatal-onset form with congenital anomalies (type I), a neonatal-onset form without congenital anomalies (type II), and a late-onset form (type III). To examine whether these different clinical forms could be explained by different ETF/ETFDH mutations that result in different levels of residual ETF/ETFDH enzyme activity, we have investigated the molecular genetic basis for disease development in nine patients representing the phenotypic spectrum of MADD. We report the genomic structures of the ETFA, ETFB, and ETFDH genes and the identification and characterization of seven novel and three previously reported disease-causing mutations. Our molecular genetic investigations of these nine patients are consistent with three clinical forms of MADD showing a clear relationship between the nature of the mutations and the severity of disease. Interestingly, our data suggest that homozygosity for two null mutations causes fetal development of congenital anomalies resulting in a type I disease phenotype. Even minute amounts of residual ETF/ETFDH activity seem to be sufficient to prevent embryonic development of congenital anomalies giving rise to type II disease. Overexpression studies of an ETFB-D128N missense mutation identified in a patient with type III disease showed that the residual activity of the mutant enzyme could be rescued up to 59% of that of wild-type activity when ETFB-D128N-transformed E. coli cells were grown at low temperature. This indicates that the effect of the ETF/ETFDH genotype in patients with milder forms of MADD, in whom residual enzyme activity allows modulation of the enzymatic phenotype, may be influenced by environmental factors like cellular temperature.     

Novel L2HGDH mutations in 21 patients with L-2-hydroxyglutaric aciduria of Portuguese origin

We studied 21 patients, from 18 families, with L-2-hydroxyglutaric aciduria (L-2-HGA), a rare neurometabolic disorder with a homogeneous presentation: progressive neurodegeneration with extrapyramidal and cerebellar signs, seizures, and subcortical leukoencephalopathy. Increased levels of L-2-hydroxyglutaric acid in body fluids proved the diagnosis of L-2-HGA in all 21 patients. We analyzed the L-2-HGA gene (L2HGDH), recently found to be mutated in consanguineous families with L-2-HGA, and identified seven novel mutations in 15 families. Three mutations appeared to be particularly prevalent in this Portuguese panel: a frameshift mutation (c.529delC) was detected in 12 out of 30 mutant alleles (40%), a nonsense mutation (c.208C>T; p.Arg70X) in 7/30 alleles (23%), and a missense mutation (c.293A>G; p.His98Arg) in four out of 30 mutant alleles (13%), suggesting that common origin may exist. Furthermore, two novel missense (c.169G>A; p.Gly57Arg, c.1301A>C; p.His434Pro) and two splice error (c.257-2A>G, c.907-2A>G) mutations were found. All the mutations presumably lead to loss-of-function with no relationship between clinical signs, progression of the disease, levels of L-2-HGA and site of the mutation. In the three remaining families, no pathogenic mutations in the L-2-HGA were found, which suggests either alterations in regulatory regions of the gene or of its intervening sequences, compound heterozygosity for large genomic deletion and, or further genetic heterogeneity.     

Holocarboxylase synthetase deficiency: Early diagnosis and management of a new case

We present a new case of holocarboxylase synthetase (HCS) deficiency, a rare autosomal recessive metabolic disorder, causing the early-onset form of multiple carboxylase deficiency. The patient was born at term of healthy consanguineous parents after an uncomplicated pregnancy. On the 2nd day of life she refused oral feeding, became tachydyspnoeic and showed excessive weight loss. Laboratory studies showed metabolic acidosis, marked lactic acidaemia, hyperammonaemia and increased urinary excretion of 3-hydroxyisovaleric acid, 3-methylcrotonyglycine, 3-hydroxypropionic acid and methylcritric acid. Peritoneal dialysis combined with oral supplementation of biotin (10 mg/day) started on the 3rd day of life resulted in rapid clinical recovery and normalisation of biochemical parameters. HCS deficiency was established in lymphocytes and skin fibroblasts. The activities of all biotin-dependent carboxylases were severely decreased in fibroblasts grown in medium with moderate biotin concentration (10^–8 mol/l) but normal in a high biotin medium (10^–5 mol/l). Mitochondrial carboxylase activities in lymphocytes were 23%–29% of mean normal during therapy with 20 mg of biotin/day, with the higher dose of 40 mg/day they were within (3-methylcrotoryl-CoA carboxylase, pyruvate carboxylase) or slightly below (propionyl-CoA carboxylase) the normal range. At the age of 3 years the patient's physical and psychomotor development are normal. Early biotin supplementation should be considered in newborns with lactic acidosis and organoaciduria until a final diagnosis has been established. Furthermore, the required individual dose of biotin has to be carefully evaluated biochemically for the individual patient.     

3-Hydroxydicarboxylic aciduria due to long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency associated with sudden neonatal death: protective effect of medium-chain triglyceride treatment

Two siblings were found to be affected by longchain 3-hydroxyacyl-CoA dehydrogenase deficiency, one of which died suddenly and unexpectedly on the 3rd day of life suffering from extreme hypoketotic hypoglycaemia. The younger sibling started to have feeding problems, lowered consciousness, and liver dysfunction at the age of 5 months. Her urine contained large amounts of C₆–C₁₄ 3-hydroxydicarboxylic acids and conjugated 3-hydroxyoctanoic acid, as verified by gas chromatography/mass spectrometry. Plasma long-chain acylcarnitine was increased. A clue to the diagnosis was given by the results of a phenylpropionic acid loading test. This revealed small, but significant amounts of conjugated 3-hydroxyphenylpropionic acid (phenylhydracrylic acid) in the patient's urine. Subsequently, the activity of long-chain 3-hydroxyacyl-CoA dehydrogenase was found to be deficient in cultured skin fibroblasts. Based on the findings obtained by a medium-chain triglyceride load, a diet enriched in this type of fat was prescribed. On this regimen the patient started to thrive, signs of cardiomyopathy disappeared, and her liver function normalized.     

Long-term clinical outcomes of cochlear implantation in children with symptomatic epilepsy

ObjectivesTo describe long-term clinical outcomes of cochlear implantation in deaf children with symptomatic epilepsy.Materials and methodsA retrospective data analysis review of patients implanted at the Cochlear Implant Center of the University of Parma, Italy, was performed, searching for implanted children with a confirmed diagnosis of symptomatic epilepsy. Clinical data, imaging findings, pre- and post-operative epilepsy pattern and EEG traces were analyzed; communicative skills were assessed using the Profile of Actual Linguistic Skills.ResultsSearch retrieved two patients affected by profound bilateral sensorineural hearing loss and symptomatic epilepsy (associated respectively with methylmalonic acidemia and cerebral palsy). After careful parental counselling both patients were offered and underwent cochlear implantation. Activation and use of cochlear implant did not determine substantial changes of pre-existing seizure pattern and EEG traces. Both patients showed substantial development of their communicative abilities.ConclusionsCochlear implantation in children with symptomatic epilepsy did not determine variations in seizure pattern or EEG traces. Both patients experienced substantial benefit from cochlear implantation.     

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??Methylmalonic aciduria is severe metabolic disorders with potential life-threatening acute complications. Early recognition of metabolic decompensation and appropriate management are critical to ensure good outcome. Plasma total homocysteine should be determined as soon as possible for the differential diagnosis of isolated MMA or combined MMA. The cornerstone of acute management is provision of enough calories and volume of body fluid. Protein restriction is necessary for the patients with isolated MMA. Cobalamin??folate and L-carnitine supplementation are important to correct the metabolic disorders. Underlying triggers should be paid attention to. Long-term management can prolong the life time and improve the quality of life. The individualized nutritional therapy and medical management are keys.     

甲基丙二酸血症1例病例报告

目的 探讨甲基丙二酸血症被误诊为糖尿病酮症酸中毒、病毒性脑炎的原因。方法 对我院收治的先后被误诊为糖尿病酮症酸中毒、病毒性脑炎的甲基丙二酸血症患儿的临床资料进行描述分析。入院先后误诊为糖尿病酮症酸中毒、病毒性脑炎,最后确诊甲基丙二酸血症。结果 本例患儿具有呼吸深大、浅昏迷、高血糖、酸中毒等临床特点,临床上极易误诊为糖尿病酮症酸中毒,而此患儿颅脑MRI表现又容易误诊为病毒性脑炎。根据串联质谱血酰基肉碱分析示丙酰肉碱、丙酰肉碱与乙酰肉碱比值增高;尿液有机酸分析示甲基丙二酸及甲基枸橼酸增高,确诊为甲基丙二酸血症。结论 MMA临床表现不具特异性,应加强MMA的早期识别能力,对可疑患儿及早行串联质谱血酰基肉碱、气相色谱-质谱尿有机酸检测,减少误诊发生。     

GCDH^-/-大鼠海马氧化应激损伤机制研究

目的探讨高赖氨酸饮食的戊二酰辅酶A脱氢酶(GCDH)基因缺陷(GCDH^-/-)大鼠氧化应激损伤机制及可能通路。方法4周龄雄性SD大鼠按照随机数字表法分为6组:野生型标准饮食(WT)组(n=6)、纯合子标准饮食(GCDH^-/-)组(n=11)、野生型高赖氨酸(WT+Lys)组(n=8)、纯合子高赖氨酸(GCDH^-/-+Lys)组(n=13)、野生型高赖氨酸加维生素E(WT+Lys+VE)组(n=7)、纯合子高赖氨酸加维生素E(GCDH^-/-+Lys+VE)组(n=12)。WT组和GCDH^-/-组给予标准饮食(常规大鼠饲料),余4组给予4.7%高赖氨酸加强饲料,自由进食水。WT+Lys+VE和GCDH^-/-+Lys+VE组于每天上午10点维生素E[100 mg/(kg·d)]灌胃1次,其余各组等量生理盐水灌胃。观察各组大鼠体质量及存活情况。干预28 d后腹腔注射100 g/L水合氯醛麻醉后断头取脑获取海马组织,通过HE染色观察大鼠海马病理形态学改变;ELISA法检测海马氧化应激指标谷胱甘肽过氧化物酶(GPx)、丙二醛(MDA)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、还原型谷胱甘肽(GSH)含量/活性;Western blotting实验检测海马P38、c-Jun N-氨基端激酶(JNK)、细胞外调节蛋白激酶(ERK)蛋白表达情况。结果(1)一般情况:GCDH^-/-+Lys组大鼠存活比例为9/13,GCDH^-/-+Lys+VE组大鼠为11/12。干预第7天开始,GCDH^-/-+Lys组、GCDH^-/-+Lys+VE组大鼠体质量均显著低于WT组,差异有统计学意义(P<0.05)。(2)应激指标检测结果:与WT组相比,GCDH^-/-+Lys组和GCDH^-/-+Lys+VE组大鼠海马组织MDA含量显著增加,差异有统计学意义(P<0.05)。与WT组比较,GCDH^-/-+Lys组大鼠GPx活性、CAT活性、SOD活性显著减弱,GSH含量显著减少,差异有统计学意义(P<0.05);与GCDH^-/-+Lys组比较,GCDH^-/-+Lys+VE组大鼠GPx活性、CAT活性、SOD活性显著增强,GSH含量显著增加,差异有统计学意义(P<0.05)。(3)Western blotting实验结果:与WT组比较,GCDH^-/-+Lys组和GCDH^-/-+Lys+VE组大鼠海马P38蛋白表达显著增加,差异有统计学意义(P<0.05);与GCDH^-/-+Lys组比较,GCDH^-/-+Lys+VE组P38蛋白表达减少,差异有统计学意义(P<0.05)。结论高赖氨酸饮食GCDH^-/-大鼠海马存在氧化应激损伤,其可能机制与激活P38启动丝裂原活化蛋白激酶信号通路有关;维生素E可降低P38表达,减轻氧化应激损伤。     

因预防接种诱发急性脑病的甲基丙二酸尿症cblA型一例

目的 报道1例因预防接种诱发急性脑病的中国甲基丙二酸尿症的cblA型病例.方法 就病例临床、血液酯酰肉碱谱、尿有机酸、甲基丙二酸尿症相关基因等特点进行分析.结果 患儿男,1岁3个月时因“间断呕吐、酸中毒、发育落后8个月”就诊.患儿生后7个月内发育正常,7个月时接种乙肝疫苗后lh出现呕吐、昏迷.临床诊断“中度脱水,电解质紊乱,代谢性酸中毒”,经补液等治疗后好转.此后,患儿发育落后,间断呕吐.1岁3个月时接种百白破疫苗,接种3h后再次出现呕吐,嗜睡,静脉补液后未见好转,7d后喘憋、呼吸困难、昏迷.患儿血液丙酰肉碱16.3μmol/L(参考值1.0 ～ 5.0μmol/L)、丙酰肉碱/游离肉碱0.27(参考值0.03 ～0.25)增高,尿甲基丙二酸(388.21 mmol/mol肌酐,参考值0.2～3.6 mmol/mol肌酐)及其代谢产物浓度显著增高,血浆总同型半胱氨酸浓度正常,符合单纯型甲基丙二酸血症,MMAA基因存在c.650 T＞A(p.L217X)和c.742 C＞T(p.Q248X)复合杂合突变,确诊为cblA型.经羟钴铵肌内注射、左卡尼汀、低蛋白饮食及特殊配方奶粉治疗后,患儿病情逐渐好转.患儿现2岁7个月,智力运动正常.结论 报道我国首例因预防接种诱发急性脑病的cblA型甲基丙二酸尿症.对疑似遗传代谢病患儿,预防接种前的代谢筛查是减少意外的关键.