Fatal neonatal cardiomyopathy associated with cataract and mitochondrial myopathy

Three patients suffering from the neonatal form of a syndrome characterized by congenital cataract, hypertrophic cardiomyopathy, and mitochondrial myopathy are described. The patients died at 7, 10 and 18 days, respectively from cardiorespiratory failure. Mitochondrial abnormalities were observed in the heart and skeletal muscle. Despite the presence of a severe lactic acidaemia pointing to a disturbed pyruvate oxidation rate in vivo, a normal pyruvate oxidation rate was demonstrated in skeletal muscle homogenates. The activities of several enzymes of the mitochondrial respiratory chain appeared to be normal, indicating an intact respiratory chain. A myoglobinopenia could be excluded. The activities of some mitochondrial enzymes and the concentration of myoglobin increase with age.Abbreviations ATP adenosine triphosphate - CrP creatine phosphate     

Congenital hypertrophic cardiomyopathy,cataract, mitochondrial myopathy and defective oxidative phosphorylation in two siblings with Sengers-like syndrome

We describe two siblings with a Sengers-like syndrome, who presented with congenital hypertrophic cardiomyopathy, infantile cataract, mitochondrial myopathy, lactic acidosis and normal mental development. A mitochondrial adenine nucleotide translocator 1 (ANT1) defect was detected since the ANT1 protein was not detectable by immmunoblotting in muscle samples of the patients. Additionally to these features of classical Sengers syndrome (OMIM 212350), we found that the mitochondrial oxidative phosphorylation, measured by biochemical analysis, was severely compromised in skeletal muscle in both children. Biochemical and morphological analysis of the fibroblasts revealed normal results. The association of significantly decreased pyruvate oxidation rates, deficient energy production and decreased multiple mitochondrial enzyme-complex activities in the muscle samples of our patients is a new finding which differs from previous results in patients with Sengers syndrome. Conclusion:we recommend a muscle biopsy and the biochemical analysis of the oxidative phosphorylation system in patients with muscle hypotonia, cardiomyopathy and congenital or infantile cataract.Abbreviations ANT1 adenine nucleotide translocator 1 - COX cytochrome c oxidase - SDH succinate dehydrogenase     

Mitochondrial myopathy with lactic acidosis and deficient activity of muscle succinate cytochrome-c-oxidoreductase

A male infant had severe muscular hypotonia from birth. Recurrent vomiting with dehydration and severe metabolic acidosis complicated the course. Elevated lactate (up to 12.3 mmol/l; n<2), pyruvate (0.4 mmol/l; n<0.05) and alanine levels were found in serum with an abnormal lactate/pyruvate ratio (>30; n<15). In urine the concentrations of lactate, pyruvate, alanine and of several intermediates of the citric acid cycle were increased. In muscle, numerous disseminated ragged red fibres were found by light microscopy; muscle fibres were found to contain subsarcolemmal aggregates of mitochondria, lipid droplets and glycogen by electromicroscopical methods. More-over, mitochondria with a typical circular arrangement of cristae were noticed.In liver homogenates normal activities of pyruvate carboxylase and pyruvate dehydrogenase complex were found; in liver mitochondria also succinate-cytochrome-c-oxidoreductase activity was normal. However, in muscle no succinate-cytochrome-c-oxidoreductase activity was detectable.The patient became increasingly lethargic and died because of sepsis at 5 months of age.     

Ultrastructural study of the childhood mitochondrial myopathic syndrome associated with lactic acidosis

The quadriceps femoris muscle and the muscularis mucosae of the rectum from two children with mitochondrial myopathic syndrome associated with lactic acidosis were studied by electron microscopy. Striking morphological abnormalities of mitochondria were noted not only in the skeletal but also in the smooth muscle cells. Endothelial cells of blood capillaries distributed in these affected muscles were so greatly swollen that the capillary lumen was almost occluded. In contrast, surface epithelial and glandular epithelial cells of the rectum contained normal mitochondria, and fenestrated capillaries in the propria mucosae remained intact. Long-term ischemia resulting from occlusive changes of the capillary wall may be responsible for the mitochondrial alterations of muscle cells.     

Deficiency of cytochromes b and aa3 in muscle from a floppy infant with cytochrome oxidase deficiency

A girl was presented suffering from generalised weakness and cardiorespiratory insufficiency. She succumbed at the age of 5 months. Lactate levels were elevated in serum, cerebrospinal fluid and urine. Histopathological examination revealed a mitochondrial myopathy. In muscle tissue the cytochrome oxydase activity was strongly reduced. The content of cytochromes b and aa₃ was very low. At autopsy a cardiomyopathy was found.     

Deficiency of the α and β subunits of pyruvate dehydrogenase in a patient with lactic acidosis and unexpected sudden death

An infant with moderate muscular hypotonia and congenital lactic acidosis died suddenly at the age of 3 months. Autopsy revealed no abnormalities responsible for this unexpected death. Measurement of mitochondrial enzymes involved in energy production indicated a severely decreased total pyruvate dehydrogenase complex (PDHC) activity in muscle tissue (0.23 nmoles · min^–1 · mg protein^–1, control range 2.8–8.7) and moderately decreased PDHC activity in fibroblasts (0.27 nmoles · min^–1 · mg protein^–1, control range 0.37–2.32). The activity of the first component E₁ (pyruvate dehydrogenase) in muscle tissue was 10 times lower than that of controls (0.008 nmoles · min^–1 · mg protein^–1, control range 0.10–0.25). The activities of dihydrolipoyl dehydrogenase (E₃) and various other mitochondrial enzymes were normal. Immunochemical analysis in skeletal muscle tissue and fibroblasts demonstrated a decrease in the amount of the and subunits of E₁. The features of this patient are compared with those of other patients reported in the literature with immunochemically confirmed combined E₁ and deficiency.     

An unusual patient with the neonatal Marfan phenotype and mitochondrial complex I deficiency

We report the case of a 16-month-old male with the neonatal appearance of Marfan syndrome (NMS), with dolichocephaly, a long midface, deep-set eyes, arachnodactyly, dislocated lenses and carciovascular abnormalities. The presence of persistent lactic acidosis led to studies which disclosed mitochondrial complex I deficiency. We speculate that this unusual association may be due to the combination of an inherited mutation affecting complex I activity along with a de novo mutation disrupting the corresponding locus and an adjacent NMS locus on the homologous autosome. The possibility that the phenotype observed in this patient is directly due to the mitochondrial defect cannot be excluded.     

Mitochondrial myopathy,encephalopathy, lactic acidosis,and stroke-like episodes (MELAS) decrease in diastolic left ventricular function assessed by echocardiography

Summary Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) are known to be associated with cardiomyopathy. Systolic and diastolic left ventricular functions were assessed by M-mode and Doppler echocardiography in four patients with MELAS and in 14 normal controls. The interventricular septal thickness and left ventricular posterior wall thickness were greater (11.0±1.6 mm vs. 5.8±0.7 mm and 11.0±2.2 mm vs. 5.9±0.8 mm) in patients with MELAS than in a control group. Parameters of systolic left ventricular functions (ejection fraction, shortening fraction, systolic time intervals, and mean Vcf) and left ventricular dimensions were not significantly different between the two groups. To assess the diastolic function, blood flow velocity across the mitral valve was measured by Doppler echocardiography and various indexes were obtained. In patients with MELAS, the impairment of diastolic left ventricular filling was demonstrated by decrease in the following indexes: peak flow velocity in the early passive filling period (E) (0.76±0.10 m/s vs. 0.94±0.09 m/s), integrated velocity for total E (10.2±1.3 vs. 13.0±0.9), the ratio of E and late atrial filling integrated velocities (1.72±0.06 vs. 2.49±0.29).     

儿童线粒体脑肌病伴高乳酸血症和卒中样发作综合征2例报告

目的：探讨线粒体脑肌病伴高乳酸血症和卒中样发作综合征(MELAS)的诊断与治疗。方法回顾性分析2例MELAS患儿的临床特征及诊疗过程。结果2例患儿主要临床表现为卒中样发作、抽搐、视物模糊、高乳酸血症；发作期头颅磁共振成像结果符合典型的MELAS综合征影像学表现；基因测序存在mtDNA的A3243G点突变；改善供能及皮质激素治疗后症状明显改善。结论 MELAS临床症状复杂多样，血乳酸及头颅磁共振成像检查有助临床诊断，确诊需要肌肉活检或基因检测，皮质激素治疗有效。     

Biochemical study in 28 children with lactic acidosis,in relation to Leigh's encephalomyelopathy

An enzymatic study of cultured skin fibroblasts was made in 28 patients with lactic acidosis. In three of these patients a diagnosis of Leigh's encephalomyelopathy was established from autopsy findings. Pyruvate decarboxylase (PDC) deficiency was found in four patients. In two of them, in whom Leigh's encephalomyelopathy was proved by autopsy, PDC activity was lower than 10% of the normal. The other two living patients, who showed 22%–25% of the normal activity, had clinical symptoms and courses different from Leigh's disease. These findings suggest that the patients with severe PDC deficiency develop Leigh's disease but those with mild deficiency may not. A deficiency of cytochrome c oxidase was found in two siblings. One of them, who was diagnosed as having Leigh's encephalomyelopathy by postmortem examination, showed a reduction of cytochrome c oxidase in the liver and brain. In the other sibling, who is living, the reduction of cytochrome c oxidase was demonstrated in the cultured skin fibroblasts and biopsied muscle. In an electron-microscopic study of biopsied muscle, two patients with mitochondrial myopathy were found. Their fundamental enzymatic defects were unclear. In two patients, in whom Leigh's disease was suspected following a brain CT, the production of ¹⁴CO₂ from [3-¹⁴C] pyruvate was found to be low; suggesting a reduced activity of the TCA cycle. In another 18 patients, the fundamental defect was not clear.Abbreviations PDC pyruvate decarboxylase - PDHC pyruvate dehydrogenase complex - PC pyruvate carboxylase - PEPCK phosphoenolpyruvate carboxykinase - SNE subacute necrotising encephalomyelopathy - EDTA ethylenediamine tetraacetic acid - PBS phosphate-buffered saline - DCA dichloroacetate - DTT dithiothreitol - CoA coenzyme A - NAD nicotinamide adenine dinucleotide - TPP thiamine pyrophosphate hydrochloride - KGDHC -ketoglutarate dehydrogenase complex - KGDC -ketoglutarate decarboxylase - LAD Lipoamide dehydrogenase     

Acute pancreatitis in an infant with lactic acidosis and a mutation at nucleotide 3243 in the mitochondrial DNA tRNALeu[UUR] gene

The A to G point mutation at position 3243 of the mitochondrial DNA tRNA^Leu(UUR)gene is commonly found in patients with the syndrome of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). A male patient was referred at 7 months with failure to thrive, developmental delay, microcephaly and hypotonia since age 2 months. He had developed lactic acidosis and increasingly frequent seizures since age 5 months. The patient was admitted at 15 months with pleural and pericardial effusions, which resolved. Three weeks later he developed evidence of pancreatitis with hyperglycemia, sudden profound increase in lactic acidosis and increased serum lipase. He died unexpectedly the next day of cardiorespiratory collapse following an acute gastro-intestinal hemorrhage. Analysis of mitochondrial DNA (mtDNA) in muscle showed heteroplasmy for the mutation MTTL1*MELAS3243G (> 95%). Infants with this mutation commonly present with failure to thrive, significant developmental delay, and hypotonia, while stroke-like episodes occur later in survivors. They usually have lactic acidosis and a high percentage of mutant mtDNA in muscle.     

Hyperalaninemia,hyperpyruvicemia and lactic acidosis due to pyruvate carboxylase deficiency of the liver; Treatment with thiamine and lipoic acid

A 16-month-old female infant with severe mental and motor retardation, clinically diagnosed as Leigh's encephalomyelopathy, forms the basis of this study. This infant was found to have lactic acidosis, low cerebrospinal fluid glucose, hyperalaninemia, and increased levels of urine lactate, pyruvate and alanine. These laboratory studies suggested an inborn error in gluconeogenesis. Further investigation revealed a low level of hepatic pyruvate carboxylase activity. The patient's elder sister who also had mental and motor deterioration was then also found to have an elevated blood lactate. These two siblings clinically and biochemically showed improvement with treatment consisting of thiamine and lipoic acid.     

以癫痫持续状态起病的线粒体脑肌病伴乳酸血症和卒中样发作患儿临床特点

目的探讨线粒体脑肌病合并乳酸血症与卒中样发作(MELAS)出现癫痫持续状态患儿的临床特点及治疗。方法回顾性分析4例以癫痫持续状态起病并最终确诊为MEILAS患儿的临床、脑电图、影像学及治疗。结果 4例患儿均以癫痫持续状态起病,血清乳酸、血氨、心肌酶升高,血钠降低,伴代谢性酸中毒;发作期及发作间期脑电图均有相应表现;头颅影像学发现基底节钙化、脑萎缩,急性期可见皮层水肿;基因检测提示mtDNA3243位点突变。结论 MELAS的癫痫发作较难控制,应尽早诊断,选择合适的抗癫痫药物及相关对症治疗,以减轻脑损伤。     

Central lactic acidosis,hyperventilation, and respiratory alkalosis: leading clinical features in a 3-year-old boy with malignant meningeal melanoma

Meningeal tumors are extremely rare in children and are diagnostically as well as therapeutically challenging. Among the least common types of malignancies in childhood is malignant melanoma, counting for less than 1% of pediatric tumors. Due to the rarity and the wide spectrum of appearance, initial clinical features may be misleading. A 3-year-old boy was referred to our hospital with symptoms of hyperventilation, dyspnoea, tachycardia, respiratory alkalosis, inarticulate speech, and fatigue. Measurement of pH in cerebrospinal fluid (CSF) yielded central lactic acidosis despite alkalosis in peripheral blood. Diagnostic imaging procedures as well as histology and immunohistochemistry revealed the diagnosis of a malignant meningeal melanoma. We hypothesize that central lactate production of the tumor nests might have induced central acidification, thus inducing hyperventilation by stimulation of central chemoreceptors. This case is a model example of the key role of central pH as an inducer/suppressor of ventilation in humans and illustrates the critical importance of central pH for regulating both ventilation and acid-base homeostasis. Thus, pH of CSF should be measured whenever a malignant brain tumor is suspected. Blüher and Schulz both contributed equally to the study.     

Functional mitochondrial heterogeneity in heteroplasmic cells carrying the mitochondrial DNA mutation associated with the MELAS syndrome (mitochondrial encephalopathy, lactic acidosis, and strokelike episodes)

Most mitochondrial DNA (mtDNA) alterations associated with human disorders are heteroplasmic, i.e. mutant mtDNA molecules coexist with normal ones within the cell. We addressed the possibility of intermitochondrial exchanges through histologic analyses of cybrid clones with increasing proportion of the MELAS (A3243G) mtDNA transfer RNA point mutation. MtDNA-dependent cytochrome c oxidase activity and protein composition as well as mitochondrial membrane potential appeared heterogeneous in individual cells from clonal heteroplasmic cell populations on the basis of confocal and electron microscopy. The number of defective cells increased with increasing mutation load. We conclude that in the presence of a heteroplasmic mtDNA mutation in the cell type that we studied, intermitochondrial molecular exchanges cannot provide an efficient even distribution of the complementing molecules such as wild-type mtDNA, transfer RNA, or protein. Mitochondria in these heteroplasmic cells cannot, therefore, be considered a single functional unit.     

Mitochondrial myopathy with lactic acidaemia,Fanconi-De Toni-Debré syndrome and a disturbed succinate: cytochrome c oxidoreductase activity

A patient with severe muscular hypotonia, failure to thrive, a metabolic acidosis and a renal tubular dysfunction is presented. The disease followed a fatal course. Blood lactate and pyruvate levels as well as lactate/pyruvate ratios were strongly elevated. There were a massive excretion of lactate in urine, a generalized hyperaminoaciduria, a proteinuria and a mellituria. The carnitine concentration was diminished in blood and muscle tissue. Biochemical investigations of skeletal muscle and liver tissue revealed a defect in the respiratory chain at the level of succinate: cytochrome c oxidoreductase. The defect could not be demonstrated in cultured fibroblasts.     

Clinical signs of heart failure are associated with increased levels of natriuretic peptide types B and A in children with congenital heart defects or cardiomyopathy

AIM: To study whether natriuretic peptide types B (BNP) and A (ANP) reflect clinical signs of heart failure (CSHF) in children with congenital heart defects or cardiomyopathy resulting in different types of haemodynamic situations, such as pressure overload in coarctation of the aorta (CoA), volume overload in ventricular septal defect (VSD) or systolic dysfunction in dilated cardiomyopathy (DCM). METHODS: Blood samples for plasma P-BNP and P-ANP were taken before procedures during regular investigation from 26 children (9 CoA, 11 VSD and 6 DCM). The ordinary paediatric cardiologist performed the cardiac evaluation and the data were retrieved from medical charts. CSHF was considered positive if two of the following criteria were fulfilled: reduced physical capacity, feeding disorders, dyspnoea, tachypnoea, hepatomegaly and oedema. The statistical methods were non-parametric. RESULTS: 0/9 children with CoA, 5/11 with VSD and 6/6 with DCM had CSHF. In children with CSHF, P-BNP and P-ANP were higher, 263 ng l(-1) (range 47.5-1300) and 303 ng l(-1) (range 168-466), than in those without CSHF, 12.3 ng l(-1) (range 4.8-30.8) and 42.9 ng l(-1) (range 13.7-189), respectively (p < 0.001, Mann-Whitney U-test), irrespective of the diagnosis. The same relationship was also found in the group of children with VSD. CONCLUSION: Plasma levels of ANP and BNP increase in children with CSHF. This increase is seen irrespective of whether it is due to systolic dysfunction, as in children with DCM, or to a volume overload with a normal systolic function, as in children with VSD.     

Rett综合征患儿线粒体结构及功能缺陷的研究

目的探讨Rett综合征患儿线粒体损伤及其基因突变的基础.方法采用细胞融合技术将6例Rett综合征患儿及9例正常对照组儿童血小板与无线粒体DNA的ρ.细胞融合,用细胞色素氧化酶电镜细胞化学方法观察融合细胞线粒体超微结构,用极谱法测定融合细胞线粒体酶复合体活性及抗氰呼吸.结果3例Rett综合征患儿的融合细胞线粒体可见空泡改变.以琥珀酸为底物时,测定Rett综合征患儿的氧耗率较正常对照组降低34%(f=3.81,P＜0.01);以苹果酸+谷氨酸与维生素C+TMPD为底物时的氧耗率相比,差异无显著性(t=0.40,P＞0.05);Rett综合征患儿抗氰呼吸显著高于正常对照组(t=4.76,P＜0.001).结论Bert综合征患儿血小板存在线粒体结构和功能的异常改变,并因而造成患儿线粒体呼吸链氧自由基增多.线粒体DNA缺陷可能在Rett综合征发病机制中起作用.     

多发性线粒体功能障碍综合征6 型1 例报告并文献复习

目的探讨PMPCB基因变异导致多发性线粒体功能障碍综合征6型(MMDS6)的临床表型和基因变异特点。方法回顾分析1例MMDS6患儿的临床资料,并结合文献进行复习。结果患儿,男,5月龄。表现为体质量不增、喂养困难、运动发育倒退、四肢肌张力低,伴高乳酸血症、心力衰竭。心脏彩超示肺动脉高压。全外显子和线粒体基因测序显示PMPCB基因c.524GA纯合核苷酸变异,父母均为杂合子,该纯合变异尚未见文献报道。结论 PMPCB基因c.524GA纯合核苷酸变异是MMDS6的致病变异。二代基因测序有助于基因型诊断。