Mutations in the MPV17 gene are responsible for rapidly progressive liver failure in infancy

MPV17 is a mitochondrial inner membrane protein of unknown function recently recognized as responsible for a mitochondrial DNA depletion syndrome. The aim of this study is to delineate the specific clinical, pathological, biochemical, and molecular features associated with mitochondrial DNA depletion due to MPV17 gene mutations. We report 4 cases from 3 ethnically diverse families with MPV17 mutations. Importantly, 2 of these cases presented with isolated liver failure during infancy without notable neurologic dysfunction. CONCLUSION: We therefore propose that mutations in the MPV17 gene be considered in the course of evaluating the molecular etiology for isolated, rapidly progressive infantile hepatic failure.     

Multiple mtDNA deletions: Clinical and molecular correlations

We studied six Italian patients harbouring multiple mitochondrial DNA (mtDNA) deletions in order to correlate clinical and molecular features. Earlier age at onset (17 vs 36 years), fewer ragged-red fibres (none vs 35%), and lower proportions of deleted mtDNAs (9 vs 33%) were found in one patient with autosomal recessive inheritance as compared to five with dominant transmission. Our findings add to the features associated with multiple deletions of mtDNA.     

乙型肝炎肝硬化失代偿期与酒精性肝硬化失代偿期患者血小板参数变化的临床分析

目的探讨不同HBV DNA水平乙型肝炎肝硬化失代偿期与酒精性肝硬化失代偿期血小板计数（PLT）及血小板平均体积（MPV）变化的临床意义。方法对36例健康人、38例HBV DNA〈105拷贝/ml乙型肝炎肝硬化失代偿期患者、36例HBV DNA〉105拷贝/ml乙型肝炎肝硬化失代偿期患者及31例酒精性肝硬化失代偿期患者的外周血PLT及MPV进行测定及分析。结果与健康人相比,乙型肝炎肝硬化及酒精性肝硬化患者PLT均下降,差异有统计学意义（P〈0.05）;与酒精性肝硬化失代偿期患者相比,HBV DNA〉105拷贝/ml乙型肝炎肝硬化失代偿期患者PLT下降,差异有统计学意义（P〈0.05）;不同HBV DNA水平的乙型肝炎肝硬化失代偿期患者PLT均下降,差异有统计学意义（P〈0.05）。与健康人相比,酒精性肝硬化失代偿期、HBV DNA〉105拷贝/ml乙型肝炎肝硬化失代偿期患者MPV均下降,差异有统计学意义（P〈0.05）;与酒精性肝硬化失代偿期患者相比,HBV DNA〉105拷贝/ml乙型肝炎肝硬化失偿代期患者MPV下降,差异有统计学意义（P〈0.05）;不同HBV DNA水平的乙型肝炎肝硬化失代偿期患者MPV变化,差异有统计学意义（P〈0.05）。结论乙型肝炎肝硬化失代偿期患者高载量HBV DNA对血小板参数降低有一定的影响。     

Clinical and molecular features of mitochondrial DNA depletion syndromes

Summary  Mitochondrial DNA depletion syndromes (MDSs) form a group of autosomal recessive disorders characterized by profoundly decreased mitochondrial DNA copy numbers in affected tissues. Three main clinical presentations are known: myopathic, encephalomyopathic and hepatocerebral. The first is associated with mutations in thymidine kinase 2 (TK2) and p53-induced ribonucleotide reductase B subunit (RRM2B); the second with mutations in succinate synthase A (SUCLA2) and B (SUCLG1); the third with mutations in Twinkle (PEO1), pol-γA (POLG1), deoxyguanosine kinase (DGUOK) and MPV17 (MPV17). In this work, we review the MDS-associated phenotypes and present our own experience of 32 MDS patients, with the aim of defining the mutation frequency of the known genes, the clinical spectrum of the diseases, and the genotype–phenotype correlations. Five of our patients carried previously unreported mutations in one of the eight MDS genes. Competing interests: None declared References to electronic databases: MDS myopathic form: OMIM #609560. MDS encephalomyopathic form: OMIM #612073. MDS, encephalomyopathic form, with renal tubulopathy: OMIM #612075. MDS hepatocerebral form: OMIM #251880. Presented at the Annual Symposium of the SSIEM, Lisbon, Portugal, 2–5 September 2008     

Mitochondrial myopathies

PURPOSE OF REVIEW: Our understanding of mitochondrial diseases (defined restrictively as defects of the mitochondrial respiratory chain) is expanding rapidly. In this review, I will give the latest information on disorders affecting predominantly or exclusively skeletal muscle. RECENT FINDINGS: The most recently described mitochondrial myopathies are due to defects in nuclear DNA, including coenzyme Q10 deficiency and mutations in genes controlling mitochondrial DNA abundance and structure, such as POLG, TK2, and MPV17. Barth syndrome, an X-linked recessive mitochondrial myopathy/cardiopathy, is associated with decreased amount and altered structure of cardiolipin, the main phospholipid of the inner mitochondrial membrane, but a secondary impairment of respiratory chain function is plausible. The role of mutations in protein-coding genes of mitochondrial DNA in causing isolated myopathies has been confirmed. Mutations in tRNA genes of mitochondrial DNA can also cause predominantly myopathic syndromes and--contrary to conventional wisdom--these mutations can be homoplasmic. SUMMARY: Defects in the mitochondrial respiratory chain impair energy production and almost invariably involve skeletal muscle, causing exercise intolerance, cramps, recurrent myoglobinuria, or fixed weakness, which often affects extraocular muscles and results in droopy eyelids (ptosis) and progressive external ophthalmoplegia.     

Clinical and genetic features of four patients with Pearson syndrome: An observational study

Pearson syndrome (PS) is a multisystem mitochondrial cytopathy arising from deletions in mitochondrial DNA. Pearson syndrome is a sporadic disease that affects the hematopoietic system, pancreas, eyes, liver, and heart and the prognosis is poor. Causes of morbidity include metabolic crisis, bone marrow dysfunction, sepsis, and liver failure in early infancy or childhood. Early diagnosis may minimize complications, but suspicion of the disease is difficult and only mitochondrial DNA gene testing can identify mutations. There is no specific treatment for PS, which remains supportive care according to symptoms; however, hematopoietic stem cell transplantation may be considered in cases of bone marrow failure.We herein describe the clinical and genetic characteristics of four patients with PS. One patient presented with hypoglycemia, two developed pancytopenia, and the final patient had hypoglycemia and acute hepatitis as the primary manifestation. All patients had lactic acidosis. Additionally, all patients showed a variety of clinical features including coagulation disorder, pancreatic, adrenal, and renal tubular insufficiencies. Two patients with pancytopenia died in their early childhood. Our experience expands the phenotypic spectrum associated with PS and its clinical understanding.     

Platelet activation in patients with Familial Mediterranean Fever

Increased platelet activation and aggregation are central processes in the pathophysiology of atherosclerosis. Increased platelet activity is associated with increased platelet volume. Mean platelet volume (MPV), a determinant of platelet function, is a newly emerging risk factor for atherothrombosis. Familial Mediterranean Fever (FMF) is an autosomal recessive disease characterized by recurrent inflammatory febrile attacks of serosal and synovial membranes. Recently few studies have shown that FMF is associated with increased atherosclerosis risk. The present study was designed to evaluate levels of MPV in FMF patients compared with healthy subjects. We selected 35 FMF patients and 35 healthy control subjects matched for age, gender, and body mass index. Metabolic parameters and MPV levels were measured in all groups. Metabolic parameters were not different among the study groups (p > 0.05). The levels of MPV were significantly higher in the FMF group than in the control group (8.6 +/- 0.9 fl vs 7.8 +/- 0.5 fl, p = 0.001). The MPV levels were negatively correlated with duration of colchicine treatment (r = -0.40, p = 0.017). Also MPV levels showed positive correlation with delay of diagnosis (r = 0.58, p = 0.001). In conclusion, our results suggest that patients with FMF tend to have an increased platelet activation. Increased platelet activity could contribute to increasing the atherosclerotic risk in FMF patients.     

Does mean platelet volume influence the attack or attack-free period in the patients with Familial Mediterranean fever?

Familial Mediterranean fever (FMF) is an autosomal recessive hereditary disease which is characterized by recurrent attacks of fever and peritonitis, pleuritis, arthritis, or erysipelas-like skin disease. Mean platelet volume (MPV) is a sign of platelet activation. There are limited studies in the literature about MPV levels in FMF patients. We aimed to investigate MPV levels during the attack period (group 1) and attack-free periods (group 2) in FMF patients, and to compare them with healthy controls (group 3). The study consisted of the data of: 60 group 1 patients, 120 group 2 patients, and 75 group 3 patients. Erythrocyte sedimentation rate, C-reactive protein, white blood cell count, platelet count, and MPV levels were retrospectively recorded from patient files. Statistical analyses showed that MPV was significantly lower in FMF patients both in group 1 and group 2 than in group 3 (p?=?0.004, p?=?0.002, respectively); however, there was no difference among group 1 and group 2 in patients with FMF (p?=?0.279). The mean platelet count of group 1 was higher than that of group 3 (p?=?0.010). In conclusion, this study results suggested that MPV level did not increase on the contrary, it decreased in patients with FMF both in group 1 and/or group 2 when compared to group 3. It was concluded that the lower MPV level was an expected result of secondary thrombocytosis in FMF patients.     

Refractory anaemia and mitochondrial cytopathy in childhood

SUMMARY. We report two cases of childhood myelodysplasia (MDS) related to a mitochondrial (mt) cytopathy that illustrate the difficulty in recognizing such disorders in patients with solely haematological signs. Both patients have refractory anaemia with ring sideroblasts and vacuolization of haemopoietic precursors. These cytological features are similar to those observed in Pearson's disease, recently identified as a mitochondrial disease, and are strongly suggestive of a mitochondrial enzyme defect. The diagnosis of mitochondrial cytopathy was established on Southern blotting of mt DNA, showing a mt DNA deletion, or on the impairment of the respiratory chain enzyme activities. The absence of cytogenic abnormalities, and the polyclonal pattern of peripheral neutrophil and lymphocyte fractions, suggest that, in mt cytopathies, MDS cannot be considered as a truly malignant disorder.     

Platelet activation in patients with Familial Mediterranean Fever

Increased platelet activation and aggregation are central processes in the pathophysiology of atherosclerosis. Increased platelet activity is associated with increased platelet volume. Mean platelet volume (MPV), a determinant of platelet function, is a newly emerging risk factor for atherothrombosis. Familial Mediterranean Fever (FMF) is an autosomal recessive disease characterized by recurrent inflammatory febrile attacks of serosal and synovial membranes. Recently few studies have shown that FMF is associated with increased atherosclerosis risk. The present study was designed to evaluate levels of MPV in FMF patients compared with healthy subjects. We selected 35 FMF patients and 35 healthy control subjects matched for age, gender, and body mass index. Metabolic parameters and MPV levels were measured in all groups. Metabolic parameters were not different among the study groups (p > 0.05). The levels of MPV were significantly higher in the FMF group than in the control group (8.6 ± 0.9 fl vs 7.8 ± 0.5 fl, p = 0.001). The MPV levels were negatively correlated with duration of colchicine treatment (r = ?0.40, p = 0.017). Also MPV levels showed positive correlation with delay of diagnosis (r = 0.58, p = 0.001). In conclusion, our results suggest that patients with FMF tend to have an increased platelet activation. Increased platelet activity could contribute to increasing the atherosclerotic risk in FMF patients.     

A survey of homozygous deletions in human cancer genomes

Homozygous deletions of recessive cancer genes and fragile sites are known to occur in human cancers. We identified 281 homozygous deletions in 636 cancer cell lines. Of these deletions, 86 were homozygous deletions of known recessive cancer genes, 17 were of sequenced common fragile sites, and 178 were in genomic regions that do not overlap known recessive oncogenes or fragile sites ("unexplained" homozygous deletions). Some cancer cell lines have multiple homozygous deletions whereas others have none, suggesting intrinsic variation in the tendency to develop this type of genetic abnormality (P < 0.001). The 178 unexplained homozygous deletions clustered into 131 genomic regions, 27 of which exhibit homozygous deletions in more than one cancer cell line. This degree of clustering indicates that the genomic positions of the unexplained homozygous deletions are not randomly determined (P < 0.001). Many homozygous deletions, including those that are in multiple clusters, do not overlap known genes and appear to be in intergenic DNA. Therefore, to elucidate further the pathogenesis of homozygous deletions in cancer, we investigated the genome landscape within unexplained homozygous deletions. The gene count within homozygous deletions is low compared with the rest of the genome. There are also fewer short interspersed nuclear elements (SINEs), long interspersed nuclear elements (LINEs), and low-copy-number repeats (LCRs). However, DNA within homozygous deletions has higher flexibility. These features may signal the presence of currently unrecognized zones of susceptibility to DNA rearrangement. They may also reflect a tendency to reduce the adverse effects of homozygous deletions by minimizing the number of genes removed.     

P53 gene mutations in acute myeloid leukemia with 17p monosomy

We looked for mutations of exons 5 to 8 of the P53 gene in 10 patients with acute myeloid leukemia (AML) and 17p monosomy, and 36 patients with AML and no cytogenetic abnormalities of 17p. DNA was analyzed by polymerase chain reaction, single-strand conformation polymorphism analysis, and nucleotide sequencing. Four of the 10 patients with 17p monosomy showed point mutation, single-nucleotide deletion, or insertion in exons 7 or 8. By contrast, only 1 of the 36 patients with AML and no cytogenetic abnormalities of 17p showed a mutation of the P53 gene in exons 5 to 8 (P less than .01). These results suggest that alterations of the P53 gene may have a role in leukemogenesis in some cases of AML. The fact that P53 gene mutations occurred more often in patients with 17p monosomy seems to support the "recessive" model of tumor suppressive activity of the P53 gene rather than the "dominant" model, in which alteration of only one allele is sufficient for the development of malignancy.     

Amplification of mitochondrial DNA in acute myeloid leukaemia

There is a long-standing interest in the possible role of mitochondria in malignancy. We sought to discover whether amplification of mitochondrial DNA (mtDNA) occurred in leukaemia, and found it was often remarkably amplified in the blast cells of acute myeloid leukaemia (AML).
We used gene dosage experiments to quantify the amount of mtDNA relative to nuclear DNA. DNA extracted from peripheral blood leucocytes or bone marrow of healthy individuals or patients was simultaneously hybridized with a probe for the mitochondrial genome and a control probe for the renin gene on human chromosome 1. Comparative densitometric ratios of approximately 1 were obtained between the two signals in 20 normal control peripheral blood samples. In contrast, comparative ratios in the range of 2–50 were observed in 25 AML samples and 13 of these showed 8-fold or greater amplification of mtDNA relative to normal peripheral blood controls. An additional four cases of AML were investigated at both presentation and remission and showed 3–10-fold amplification of mtDNA at presentation, but no amplification when in clinical remission. 18 cases of chronic granulocytic leukaemia (CGL) were also studied in chronic phase and showed mtDNA dosage levels equivalent to normal peripheral blood controls. However, 8/9 CGL patients showed mtDNA amplification during transformation from chronic phase. We conclude that amplification of mtDNA is an invariable feature of acute myeloid leukaemia and that it may be a useful marker for detecting transformation of CGL.     

Mean platelet volume and mortality in patients with alcohol use disorder

Several recent studies have pointed out the relationship of platelet size with increased mortality or adverse clinical course. Most studies show that increased mean platelet volume (MPV) may be associated with a deleterious outcome in different settings such as sepsis or neoplasia, whereas other researchers have found the opposite. In inflammatory conditions there is an altered secretion of several cytokines, some of them exerting a marked influence on platelet biogenesis and/or on platelet activation and aggregation. Alcohol use disorder is a chronic situation characterized by a protracted low-grade inflammation. In this study we analyze the relationship between proinflammatory cytokines and MPV and their relationships with mortality in patients with alcohol abuse. We determined serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 and routine laboratory variables among 184 patients with alcohol use disorder admitted to our hospital and followed-up for a median of 42 months. We found that MPV was inversely related to TNF-α (ρ=-0.34), and directly to IL-8 (ρ=0.32, p<0.001 in both cases) and to IL-6 (ρ=0.15; p = 0.046). Reduced MPV was related both with short-term (<6 months) and long-term mortality. Conclusion: These results suggest that inflammatory cytokines are strongly related to MPV. A low MPV is associated with a poor prognosis among patients with alcohol use disorder.     

The routine measurement of platelet volume: a comparison of aperture-impedance and flow cytometric systems

The effect of dipotassium ethylenediaminetetraaceticacid (EDTA) on the platelet count and mean volume (MPV) was evaluated using two routine measurement systems, a Coulter S Plus Phase 1 (S+) and a Technicon H6000 (H6000). In normal subjects (n = 29) MPV increased by 17% during 39 h storage in EDTA when measured by the S+. In contrast MPV decreased by 22% when measured by the H6000. MPV differences of up to 40% were observed between the two systems. Concomitant platelet counts, in both systems, changed by less than 4%. Using the anticoagulant sodium citrate and prostaglandin E1 (Na-citrate/PGE1 there were no significant changes in MPV measured by the S+ during 7 h storage, although a linear decrease in platelet count was observed. A decrease in H6000 MPV was observed whether the blood was stored in EDTA or Na-citrate/PGE1. Methodology, anticoagulation and storage time all influence MPV. Until these determinants are standardized the clinical value of MPV cannot be assessed.     

Megaloblastic pancytopenia vis-à-vis non-megaloblastic pancytopenia: is mean platelet volume useful discriminating indicator

Introduction: Megaloblastic anaemia may present with pancytopenia and clinically mimic other causes of pancytopenia including myelodysplastic syndrome or aplastic anaemia. Bone marrow examination may be required for precise differentiation. The study was conducted to evaluate the role of mean platelet volume (MPV) to discriminate between pancytopenia due to megaloblastic anaemia or non‐megaloblastic causes. Methods: A total of 268 cases of pancytopenia were divided into megaloblastic and non‐ megaloblastic group depending on clinical, laboratory and bone marrow examination. Mean MPV was statistically analyzed in both the groups along with comparison with healthy controls. Results: The mean MPV in 88 cases of megaloblastic group (7.97 fl) was although statistically significantly higher than mean MPV in 180 cases of non‐megaloblastic group (7.04 fl) with P value <0.05 but had limited sensitivity and specificity to discriminate megaloblastic and non‐megaloblastic pancytopenia (cut off of 7.45 fl was 63.6% sensitive and 67.3% specific as observed by receptor operating characteristic curve analysis).The mean MPV in aplastic/hypocellular marrow and acute leukaemia category of non‐megaloblastic group was significantly lower than megaloblastic group of pancytopenia (P value <0.05). MPV was also significantly lower in non‐megaloblastic pancytopenia as compared to controls (P < 0.001) while there was no statistical difference in MPV between megaloblastic pancytopenia and controls (P < 0.057). Conclusion: MPV has limited sensitivity and specificity to discriminate between megaloblastic and non‐megaloblastic pancytopenia. Pancytopenia due to aplastic/hypocellular marrow and acute leukaemia has significantly lower MPV than megaloblastic group while other pancytopenic cases do not show any statistical difference in MPV from megaloblastic pancytopenia.     

急性心肌梗死患者心室血栓与血小板体积和数量的相关性

目的分析急性心肌梗死(AMI)患者并发左心室血栓与平均血小板体积(MPV)和血小板计数(PLT)的相关性。方法回顾性分析2007年1月至2011年4月在阜外心血管病医院住院治疗的69例AMI并心室血栓形成患者,及138例与之年龄匹配(1∶2)的无心室血栓形成的AMI患者。比较两组患者入院时和入院后第6～8天两个时间点的MPV和PLT变化特点,以及分析MPV和PLT的相关性。结果两组患者入院时MPV差异无统计学意义[(10.3±1.0)fl比(10.3±0.8)fl,P=0.854],入院后第6～8天心室血栓组患者的MPV明显高于无心室血栓组[(11.1±1.7)fl比(10.7±0.7)fl,P=0.029]。入院时和入院后第6～8天PLT在两组间差异均无统计学意义(P=0.587、0.807)。入院后第6～8天患者MPV与PLT的关联表现为线性关系。结论 AMI患者MPV增大可能与心室血栓形成相关。     

Novel spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis in ethnic Omani patients

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive immune disorder, characterized by fever, hepatosplenomegaly, pancytopenia, hypertriglyceridemia, hypofibrinogenemia, markedly elevated levels of inflammatory cytokines, and impaired cytotoxic activity of lymphocytes. FHL is often fatal in early infancy. Histologic features include organ infiltration by activated macrophages and lymphocytes. Four genetic loci (FHL1, 2, 3, and 4) have been identified, of which FHL2 involves mutations in the perforin gene and is present in 20-50% of patients with FHL. We herein report the first comprehensive molecular analysis of 16 unrelated cases of FHL in ethnic Omanis. Using direct DNA sequencing analysis in 11 families, seven different mutations were identified in the coding region of the perforin gene, of which five were novel. Perforin gene defects do not seem to be involved in one-third of the cases of FHL in ethnic Omanis.     

红细胞分布宽度、平均血小板体积与早发冠心病的相关性

目的探讨红细胞分布宽度(RDW)、平均血小板体积(MPV)在早发冠心病人群中的分布特征及其与冠状动脉病变严重程度的关系,评价RDW、MPV对早发冠心病的诊断价值。方法收集因胸痛发作疑诊冠心病且男性55岁、女性65岁的患者407例,经冠状动脉造影(CAG)确诊早发冠心病组309例,余98例为正常对照组。比较2组及早发冠心病各疾病亚组间的RDW、MPV水平,分析RDW、MPV与冠状动脉病变严重程度(Gensini评分)的相关性及早发冠心病的独立危险因素。结果早发冠心病组RDW、MPV水平明显高于正常对照组(P0.05),RDW、MPV在急性心肌梗死(AMI)组、不稳定型心绞痛(UAP)组和稳定型心绞痛(SAP)组均高于正常对照组(P0.05)。早发冠心病组RDW、MPV与Gensini评分之间存在正相关(r分别为0.246、0.199,P0.05);多因素Logistic回归分析显示RDW(OR=3.373,95%CI:2.197～6.359,P0.001)和MPV(OR=1.353,95%CI:1.074～1.705,P=0.010)是早发冠心病的独立危险因素。R0C曲线分析发现,RDW诊断早发冠心病的界点值为12.25%(敏感性69%,特异性72%),MPV诊断早发冠心病的界点值为8.55 fl(敏感性91%,特异性37%)。结论 RDW、MPV与早发冠心病的临床类型及冠状动脉病变的严重程度有关,是早发冠心病的独立危险因素,为早发冠心病的诊断提供一定依据。     

Novel insertion frameshift mutation of the LH receptor gene: problematic clinical distinction of Leydig cell hypoplasia from enzyme defects primarily affecting testosterone biosynthesis

Leydig cell hypoplasia (LCH) is a rare autosomal recessive condition that interferes with normal development of male external genitalia in 46,XY individuals and is caused by inactivating mutations of the LH receptor gene. The clinical and biochemical diagnostic parameters of LCH are not always specific and may therefore show significant overlap with other causes of insufficient testicular steroid biosynthesis. We have studied a 46,XY newborn with completely female external genitalia and palpable testes. Due to an increased basal serum ratio of androstenedione/testosterone, 17 beta-hydroxysteroid dehydrogenase type 3 (17 beta-HSD 3) deficiency was initially suspected. DNA analysis of the corresponding HSD17B3 gene, however, showed no abnormalities in the entire coding region. In contrast, direct sequencing of the LH receptor gene revealed a novel homozygous single nucleotide insertion in exon 11 (codon A589fs) producing a frame shift in the open reading frame predicting for premature termination of translation 17 amino acids downstream. From the genetic perspective, this mutation represents the first frame shift mutation in the LH receptor gene ever reported to date. From the clinical standpoint, LCH should always be considered in the differential diagnosis as steroid profiles may not be informative. Therefore, molecular genetic analysis should be warranted for androgen biosynthesis defects in all cases.