cbIC型甲基丙二酸血症23例患儿临床及基因特点分析

目的分析23例cbIC型甲基丙二酸血症(合并同性半胱氨酸尿症)患儿临床表现、基因突变类型、治疗效果和预后特点,以提高对该病的临床认识,为该病精准治疗提供依据。方法回顾整理2012年1月~2016年12月青岛地区通过新生儿串联质谱筛查诊断的23例cbIC型甲基丙二酸血症患儿临床资料,完善辅助检查、基因检测结果及诊疗效果,按临床表现分析重型、轻型和中间型,探讨患儿临床表型和基因突变类型以及疗效的关系。结果 cbIC型甲基丙二酸血症患儿临床差异较大,个体表现多样,重型患者基因突变以c.609GA/c.658_660del AAG为主,临床多新生儿期发病,以抽搐、代谢危象、喂养困难、体重不增为主要表现;轻型患者基因突变以c.482GA/c.658_660del AAG、c.482GA/c.609GA为主,早期确诊后及时治疗临床表型基本正常。采用羟钴胺素可明显改善cbIC型甲基丙二酸血症的临床症状,但患儿预后仍与基因型有密切关系。结论 c.609GA、c.658_660del AAG是青岛地区cbIC型甲基丙二酸血症重型患者主要突变,c.482GA是轻型患者的主要突变;新生儿串联质谱筛查是早期发现MMA患者的有力手段,结合基因突变类型给予不同MMA患者个性化治疗,是提高患者存活率和治疗效果的最佳途径。     

15例甲基丙二酸血症患儿临床特征和基因突变分析

目的分析15例甲基丙二酸血症(MMA)患儿临床特征和基因突变,为家系遗传咨询、产前诊断和新生儿筛查提供依据。方法选择15例先证者MMA患儿,其中男性7例,女性8例;年龄63 h～11岁,中位年龄2岁;cblC型12例(1个月～11岁,中位年龄1岁6个月),mut型3例(年龄63 h、3 d和3岁)。分析其临床资料。应用液相色谱和串联质谱技术对患儿尿液和血液代谢物进行筛查,应用Sanger测序方法结合高通量测序对患儿家系进行相关基因检测和分析。结果 15例MMA患儿临床表现各异,累及全身多系统,常见临床表型主要为癫痫、水电解质紊乱、贫血、粒细胞缺乏和呼吸性/代谢性酸中毒等。在12例cblC型患儿钴胺素代谢相关C基因(MMACHC)中共检测出8种基因突变,包括7种错义突变和1种缺失突变,其中最常见的为c.658-660delAAG、c.609G A和c.80A G,分别占25%(6/24)、20.83%(5/24)和20.83%(5/24)。在3例mut型患儿甲基丙二酰辅酶A变位酶基因(MUT)中共检测出5种基因突变,包括3种错义突变、2种剪接位点突变。结论 MMA亚型cblC型与表型存在一定相关性,mut型临床表现比cblC型更为严重。该研究结果丰富了MMA相关基因突变谱,为遗传咨询、产前诊断和新生儿筛查提供了依据。     

甲基丙二酸血症cblA型12例分析

目的探讨甲基丙二酸血症(methylmalonic acidemia,MM A)cblA型患儿的临床特点、基因变异类型及治疗效果。方法分析12例cblA型MMA患儿的临床表现,治疗方案及预后,对先证者及其父母进行MMAA基因的变异分析。结果MMA cblA型患儿主要表现为呕吐、气促和嗜睡。维生素B12治疗对11例(91.7%)患儿有效。治疗后患儿血丙酰肉碱、丙酰肉碱与乙酰肉碱比值、尿甲基丙二酸及甲基枸椽酸水平均显著降低,差异有统计学意义(均P<0.05)。8例患儿生长发育正常(66.7%),4例智力运动发育落后(33.3%)。检测到14种MMAA基因变异,包括6种新变异:c.54delA(p.A19Hfs*43)、c.275G>A(p.G92V)、c.456delT(p.G153Vfs*8)、c.667dupA(p.T223Nfs*4)、c.1114C>T(p.Q372X)和c.1137_1138delCA(p.F379Lfs*27)e最常见的变异为c・365T>C(p.L122P)(29.2%)。结论cblA型MMA患儿主要表现为呕吐、气促和嗜睡,大部分患儿为维生素B12治疗有效型。c.365T>C为中国MMAA基因的常见变异。     

甲基丙二酸尿症一家系MMACHC基因突变分析

目的 研究甲基丙二酸尿症(methymalonic aciduria,MMA)MMACHC基冈的突变.方法 应用聚合酶链反应及DNA直接测序技术对甲基丙二酸尿症一家系进行MMACHC基因突变位点检测,并与50名健康人的MMACHC基冈进行对照.结果 患者及其父亲的MMACHC基因中检测到一个新的整码突变,MMACHC基因第2外显子146_154缺失CCTTCCTGG,导致P.49_51位缺失丙氨酸苯丙氨酸亮氨酸(AFL),50名对照者的等位基因无此突变.结论 MMACHC基因的146_154缺失CCTTCCTGG也可能是该家系引起甲基丙二酸尿症的病因.     

单纯型甲基丙二酸血症家系MUT基因变异的分析及产前诊断CSCD

目的对20个单纯型甲基丙二酸血症家系MUT基因的变异进行测序分析,为家系产前诊断提供依据。方法应用PCR产物直接测序法对20例单纯型甲基丙二酸血症患儿及其父母的MUT基因进行变异检测和分析,明确基因变异情况,并对9名孕妇进行产前诊断。结果20例患儿的家系共检测出19种MUT基因变异,最常见的变异为C.323G〉A（P．Arg108His）、c．1106G〉A（P．Arg369His）、C．729_730insTT（P．D244Lfs＊39）和c．1107dupT（P．T370Yfs＊22）。C．920_923delTCTT（P．F307SIs＊6）、C．419T〉C（P．Leu140Pro）和C．613G〉A（P．Glu205Lys）为未报道过的新变异。Polyphen2和Mutationtaster软件预测这3个变异均可能致病。产前诊断结果显示1例胎儿未检测到MUT基因变异,3例胎儿为MUT基因杂合变异携带者,5例胎儿为MUT基因复合杂合变异或纯合变异患儿。MUT基因正常或杂合变异携带者胎儿的家系选择继续妊娠,而MUT基因纯合变异或复合杂合变异胎儿的家系均选择终止妊娠,胎儿娩出后随访结果与产前诊断结果一致。结论MUT基因突变分析结果为家系的产前诊断提供了依据,新变异的检出丰富了MUT基因突变谱。     

济宁地区有机酸血症筛查阳性病例基因突变特征

目的 了解济宁地区有机酸血症的患病率和基因突变规律。方法 采集2014年7月14日至2019年12月31日出生的新生儿血样,用串联质谱技术测定血中氨基酸和肉碱水平,筛查有机酸血症,提取筛查阳性新生儿外周血DNA,用核酸质谱和二代测序进行基因突变分析,用Sanger测序验证。结果 从608818例新生儿中筛查出有机酸血症146例,共包含7种疾病,以甲基丙二酸血症和3-甲基巴豆酰辅酶A羧化酶缺乏症最常见,分别占70.55%和15.75%。甲基丙二酸血症cblC型病例中检出的MMACHC基因纯合突变占22.37%(17/76),复合杂合突变占73.68%(56/76),杂合突变占3.95%(3/76),常见的突变位点为c.609G>A(p.W203*)、c.482G>A(p.R161Q)、c.658-660del(p.K220del)。甲基丙二酸血症MUT基因复合杂合占92.30%(24/26),杂合占7.69%(2/26),常见的突变位点c.1106G>A(p.R369H)。甲基丙二酸血症cblA型为MMAA基因位点c.742C>T(p.Q248*)的纯合突变。3-...     

应用串联质谱技术进行河南省新生儿甲基丙二酸血症的筛查结果分析

目的探讨串联质谱技术(MS/MS)在河南省新生儿甲基丙二酸血症(MMA)筛查中的作用和意义,统计并了解我省MMA的发病情况。方法收集2012年12月至2018年12月的河南省出生72h后经充分哺乳的新生儿820 337例,采足跟血,制成干燥血滤纸片,MS/MS法检测血片丙酰基肉碱(C3)、游离肉碱(C0)、乙酰基肉碱(C2)、蛋氨酸(MET)、C3/C2、C3/C0、C3/MET。尿GC-MS检测尿液甲基丙二酸(MMA)、3-羟基丙酸、甲基枸橼酸的水平变化,结合血同型半胱氨酸(HCY)及基因检测以明确诊断。结果新筛共确诊174例MMA。其MS/MS结果显示C3增高的有144例,C3/C2增高的有171例。C3/MET增高的有148例。C3正常的为30例。尿MMA增高的有174例,甲基枸橼酸增高的有104例,3-羟基丙酸增高的有69例。HCY增高的有156例。基因检测显示156例为MMACHC型,即为B12有效型,其中c.609GA突变出现频率最高。18例为MUT型,为B12无效型,其中c.1663GA突变出现频率最高。结论 MMA是河南省新生儿遗传代谢病筛查中最常见的有机酸血症,其发病率为1/4714。且血C3/C2及尿MMA增高,对诊断MMA更具有特异性。MMA大部分为B12有效型,且MMACHC型MMA是MMA中最主要的类型,C3/MET和HCY的增高可以很好的提示MMA的基因分型为MMACHC型。通过MSMS筛查,多数患儿在无症状前就能被筛查出来,且可以在基因结果出来之前即可进行有效的治疗,是提高患者存活率和治疗效果的有效途径。     

二例甲基丙二酸血症患儿基因突变分析并中国人群MMACHC基因c.609G>A突变频率检测

目的对2例合并型甲基丙二酸血症患儿进行基因突变和临床表型分析,检测中国人群MMACHC基因c.609GA突变携带频率,建立这一突变的快速检测方法。方法收集整理患儿临床资料,提取患儿及家属基因组DNA,扩增其MMACHC基因外显子及外显子与内含子交接区序列,进行sanger测序并与正常序列进行比对;利用PCR-RFLP方法检测200例正常儿童MMACHC基因c.609GA突变携带率。结果在1例患儿MMACHC基因中检测到复合杂合突变:c.80AG(p.Q27R)和c.609GA(p.W203X);在另1患儿MMACHC基因中检测到纯合突变c.609GA(p.W203X)。在200例正常儿童MMACHC基因中未检测到c.609GA突变,推测中国人群c.609GA携带频率低于0.5%(1/200)。结论 MMACHC基因c.609GA突变是合并型MMA的致病性突变,同时也是中国人群热点突变,其所导致的MMA患儿发病较早,病情较重,中国人群中由这一突变引起的合并型MMA的发生率低于1∶40 000(1/200*1/200)。     

甲基丙二酸血症串联质谱敏感指标分析

目的 通过分析甲基丙二酸血症(MMA)串联质谱的异常敏感指标结果,为MMA的筛查和诊断提供更好的依据.方法 回顾性分析2016-2019年于北京新筛中心确诊的MMA患儿的串联质谱结果,了解该疾病相关的检测指标及其各指标的敏感度.结果 在筛查的63858名新生儿中,共确诊6例MMA患儿,发病率为1/10643.指标中丙酰...     

三例酪氨酸血症Ⅰ型患者的临床表现及基因突变分析

目的 分析酪氨酸血症Ⅰ型患儿的临床资料和基因突变情况,探讨基因型与临床表型的关系.方法 采用串联质谱检测血酪氨酸、苯丙氨酸和琥珀酰丙酮水平,气相质谱检测尿琥珀酰丙酮及有机酸,确诊酪氨酸血症工型,对确诊患儿进行基因突变检测分析.结果 确诊的3例患者中2例为急性型,1例为亚急性型,表现为肝肿大,血酪氨酸和琥珀酰丙酮显著增高.基因突变分析检测到5种突变类型:c.455G>A(W152X)、 c.520C>T(R174X)、c.974_976delCGAinsGC、c.1027 G>A(G343R)、c.1100 G>A(W367X),其中c.455G>A(W152X)、c.974_976delCGAinsGC、c.1100 G>A(W367X)为新突变.结论 应用串联质谱检测血酪氨酸及琥珀酰丙酮水平、气相质谱检测检测尿琥珀酰丙酮可诊断酪氨酸血症工型.基因突变检测结果为遗传咨询以及后续研究提供依据.     

Spectrum of mutations in mut methylmalonic acidemia and identification of a common Hispanic mutation and haplotype

Cobalamin nonresponsive methylmalonic acidemia (MMA, mut complementation class) results from mutations in the nuclear gene MUT, which codes for the mitochondrial enzyme methylmalonyl CoA mutase (MCM). To better elucidate the spectrum of mutations that cause MMA, the MUT gene was sequenced in 160 patients with mut MMA. Sequence analysis identified mutations in 96% of disease alleles. Mutations were found in all coding exons, but predominantly in exons 2, 3, 6, and 11. A total of 116 different mutations, 68 of which were novel, were identified. Of the 116 different mutations, 53% were missense mutations, 22% were deletions, duplications or insertions, 16% were nonsense mutations, and 9% were splice-site mutations. Sixty-one of the mutations have only been identified in one family. A novel mutation in exon 2, c.322C>T (p.R108C), was identified in 16 of 27 Hispanic patients. SNP genotyping data demonstrated that Hispanic patients with this mutation share a common haplotype. Three other mutations were seen exclusively in Hispanic patients: c.280G>A (p.G94R), c.1022dupA, and c.970G>A (p.A324T). Seven mutations were seen almost exclusively in black patients, including the previously reported c.2150G>T (p.G717V) mutation, which was identified in 12 of 29 black patients. Two mutations were seen only in Asian patients. Some frequently identified mutations were not population-specific and were identified in patients of various ethnic backgrounds. Some of these mutations were found in mutation clusters in exons 2, 3, 6, and 11, suggesting a recurrent mutation.     

Molecular basis of methylmalonyl-CoA mutase apoenzyme defect in 40 European patients affected by mut(o) and mut- forms of methylmalonic acidemia: identification of 29 novel mutations in the MUT gene

Methylmalonyl-CoA mutase (MCM) apoenzyme deficiency is a rare metabolic disease that may result in distinct biochemical phenotypes of methylmalonic acidemia (MMA), namely mut(o) and mut-. We analyzed a cohort of 40 MCM-deficient patients with MMA affected by either the mut(o) or the mut- form of the disease. By direct sequencing of cDNA and gDNA of the MUT gene, we detected 42 mutations, 29 of which were novel mutations. These included five frameshift mutations (insertion, deletion, or duplication of a single nucleotide), five sequence modifications in consensus splice sites, six nonsense and 12 missense mutations, and a large genomic deletion including exon 12. We explored how the 12 novel missense mutations might cause the observed phenotype by mapping them onto a three-dimensional model of the human MCM generated by homology with the P. shermanii enzyme. In this work we update the spectrum of MCM mutations (n=84), and then discuss their prevalence and distribution throughout the coding sequence in relation to the enzyme structure.     

Protein destabilization and loss of protein‐protein interaction are fundamental mechanisms in cblA‐type methylmalonic aciduria

Mutations in the human MMAA gene cause the metabolic disorder cblA‐type methylmalonic aciduria (MMA), although knowledge of the mechanism of dysfunction remains lacking. MMAA regulates the incorporation of the cofactor adenosylcobalamin (AdoCbl), generated from the MMAB adenosyltransferase, into the destination enzyme methylmalonyl‐CoA mutase (MUT). This function of MMAA depends on its GTPase activity, which is stimulated by an interaction with MUT. Here, we present 67 new patients with cblA‐type MMA, identifying 19 novel mutations. We biochemically investigated how missense mutations in MMAA in 22 patients lead to disease. About a third confer instability to the recombinant protein in bacterial and human expression systems. All 15 purified mutant proteins demonstrated wild‐type like intrinsic GTPase activity and only one (p.Asp292Val), where the mutation is in the GTP binding domain, revealed decreased GTP binding. However, all mutations strongly decreased functional association with MUT by reducing GTPase activity stimulation upon incubation with MUT, while nine mutant proteins additionally lost the ability to physically bind MUT. Finally, all mutations interfered with gating the transfer of AdoCbl from MMAB to MUT. This work suggests loss of functional interaction between MMAA and MUT as a disease‐causing mechanism that impacts processing and assembly of a cofactor to its destination enzyme.     

Genetic analysis of three genes causing isolated methylmalonic acidemia: identification of 21 novel allelic variants

Isolated methylmalonic aciduria (MMA) is an inborn error of metabolism due to the impaired isomerization of l-methylmalonyl-CoA to succinyl-CoA. This reaction is catalyzed by the mitochondrial protein methylmalonyl-CoA mutase (MCM, EC 5.4.99.2), an adenosylcobalamin-dependent enzyme. Four different forms of isolated MMA have been described: mut MMA associated with defects in the MCM apoenzyme, and phenotypically divided into two subtypes mut- and mut0 MMA, and three different defects involved in the synthesis of the active form of the cofactor adenosylcobalamin, termed cbl MMA, and classified into three different complementation groups cblA, cblB, and cblH associated with defects in the MMAA and MMAB genes and with an unidentified protein, respectively. In this work we describe the genetic analysis of 25 MMA patients, mainly from Spain. Using biochemical and cellular approaches our patients have been classified, identifying 13 mut MMA, 7 cblA, 2 cblB, and 3 noncblA, noncblB deficient patients. cDNA and genomic DNA sequence analysis of the MUT, MMAA, and MMAB genes have allowed us to identify 27 different changes, 21 novel ones. Among the missense mutations identified in the MUT gene only one, the c.970G>A (p.A324T) variant located in the substrate binding domain is likely a mut- mutation. The remaining missense mutations c.326A>G (p.Q109R), c.983T>C (p.L328P), c.1846C>T (p.R616C), and c.1850T>G (p.L617R) are probably mut0. In the MMAA patients analyzed, frameshift mutations are prevalent. We have explored the genotype-phenotype correlation for this clinically heterogeneous disease.     

Molecular and phenotypic characteristics of seven novel mutations causing branched‐chain organic acidurias

Specific mitochondrial enzymatic deficiencies in the catabolism of branched‐chain amino acids cause methylmalonic aciduria (MMA), propionic acidemia (PA) and maple syrup urine disease (MSUD). Disease‐causing mutations were identified in nine unrelated branched‐chain organic acidurias (BCOA) patients. We detected eight previously described mutations: p.Asn219Tyr, p.Arg369His p.Val553Glyfs*17 in MUT, p.Thr198Serfs*6 in MMAA, p.Ile144_Leu181del in PCCB, p.Gly288Valfs*11, p.Tyr438Asn in BCKDHA and p.Ala137Val in BCKDHB gene. Interestingly, we identified seven novel genetic variants: p.Leu549Pro, p.Glu564*, p.Leu641Pro in MUT, p.Tyr206Cys in PCCB, p.His194Arg, p.Val298Met in BCKDHA and p.Glu286_Met290del in BCKDHB gene. In silico and/or eukaryotic expression studies confirmed pathogenic effect of all novel genetic variants. Aberrant enzymes p.Leu549Pro MUT, p.Leu641Pro MUT and p.Tyr206Cys PCCB did not show residual activity in activity assays. In addition, activity of MUT enzymes was not rescued in the presence of vitamin B12 precursor in vitro which was in accordance with non‐responsiveness or partial responsiveness of patients to vitamin B12 therapy. Our study brings the first molecular genetic data and detailed phenotypic characteristics for MMA, PA and MSUD patients for Serbia and the whole South‐Eastern European region. Therefore, our study contributes to the better understanding of molecular landscape of BCOA in Europe and to general knowledge on genotype–phenotype correlation for these rare diseases.     

Genetic and biochemical approach to early prenatal diagnosis in a family with mut methylmalonic aciduria

Genetic and biochemical prenatal diagnosis was performed at 11 weeks of gestation in a family with a proband affected by mut methylmalonic aciduria (MMA) and homozygotes for the MUT gene c.643G>A (p.Gly215Ser) mutation. Both chorionic villus and amniotic fluid samples were used. The presence of high levels of methylmalonic acid and propionylcarnitine determined by gas chromatography/mass spectrometry and LC/MS/MS analysis, respectively, and the identification of the p.Gly215Ser at a homozygous level in foetal DNA allowed a certain, rapid and early diagnosis. To our knowledge, this is the first mut MMA prenatal diagnosis carried out by genetic and biochemical approach.     

Clinical and molecular findings in Thai patients with isolated methylmalonic acidemia

Isolated methylmalonic acidemia (MMA) is a genetically heterogeneous organic acid disorder caused by either deficiency of the enzyme methylmalonyl-CoA mutase (MCM), or a defect in the biosynthesis of its cofactor, adenosyl-cobalamin (AdoCbl). Herein, we report and review the genotypes and phenotypes of 14 Thai patients with isolated MMA. Between 1997 and 2011, we identified 6 mut patients, 2 cblA patients, and 6 cblB patients. The mut and cblB patients had relatively severe phenotypes compared to relatively mild phenotypes of the cblA patients. The MUT and MMAB genotypes were also correlated to the severity of the phenotypes. Three mutations in the MUT gene: c.788G>T (p.G263V), c.809_812dupGGGC (p.D272Gfs*2), and c.1426C>T (p.Q476*); one mutation in the MMAA gene: c.292A>G (p.R98G); and three mutations in the MMAB gene: c.682delG (p.A228Pfs*2), c.435delC (p.F145Lfs*69), and c.585-1G>A, have not been previously reported. RT-PCR analysis of a common intron 6 polymorphism (c.520-159C>T) of the MMAB gene revealed that it correlates to deep intronic exonization leading to premature termination of the open reading frame. This could decrease the ATP:cobalamin adenosyltransferase (ATR) activity resulting in abnormal phenotypes if found in a compound heterozygous state with a null mutation. We confirm the genotype-phenotype correlation of isolated MMA in the study population, and identified a new molecular basis of the cblB disorder.     

Expression and kinetic characterization of methylmalonyl-CoA mutase from patients with the mut- phenotype: evidence for naturally occurring interallelic complementation

L-Methylmalonyl-CoA mutase (MUT) is an adenosylcobalamin (AdoCbl)- requiring mitochondrial matrix enzyme that catalyzes the isomerization of L-methylmalonyl-CoA to succinyl-CoA. Inherited defects in the gene encoding this enzyme result in the mut forms of methylmalonic acidemia. Expression of mature human MUT cDNA in Escherichia coli at a post- induction cultivation temperature of 12 degrees C, rather than 37 degrees C, led to the folding of the majority of the synthesized protein to a soluble form, with an activity of 0.2-0.3 U/mg protein in the cell-free extract, 10-15 times higher than that in human liver homogenate. Six missense mutations, producing the amino acid changes G94V, Y231N, R369H, G623R, H678R and G717V, were detected in MUT cDNA of patients suffering from the mut- form of methylmalonic acidemia, resulting from defective AdoCbl binding. Two (G623R and G717V) had been reported in other patients. Three (G94V, Y231N and R369H) are the first changes in the NH2-terminal part of the enzyme reported to cause the mut- phenotype. Enzymes with the mutations were individually expressed, and their kinetic parameters were generally in accord with published biochemical data from extracts of fibroblasts from these patients. The mutations increased the K(m) for AdoCbl by 40- to 900-fold, while V(max) values varied from 0.2% to nearly 100% of that of wild-type protein. In one case of a doubly heterozygous cell line, however, neither of the constituent mutant enzymes had a K(m) corresponding to the lower of the two estimated from the extract data. This finding may reflect the natural occurrence of interallelic complementation in vivo in this cell line.      

Clinical and molecular findings in 37 Turkish patients with isolated methylmalonic acidemia

Background/aim Isolated methylmalonic acidemia (MMA) is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 or mut– enzymatic subtype), a defect of its cofactor adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. While onset of the disease ranges from the neonatal period to adulthood, most cases present with lethargy, vomiting and ketoacidosis in the early infancy. Major secondary complications are; growth failure, developmental delay, interstitial nephritis with progressive renal failure, basal ganglia injury and cardiomyopathy. We aimed to demonstrate clinical and molecular findings based on long-term follow up in our patient cohort. Materials and methods The study includes 37 Turkish patients with isolated MMA who were followed up for long term complications 1 to 14 years. All patients were followed up regularly with clinical, biochemical and dietary monitoring to determine long term complications. Next Generation Sequencing technique was used for mutation screening in five disease-causing genes including; MUT , MMAA , MMAB , MMADHC , MCEE genes. Mutation screening identified 30 different types of mutations. Results While 28 of these mutations were previously reported, one novel MMAA mutation p.H382Pfs*24 (c.1145delA) and one novel MUT mutation IVS3+1G>T(c.752+1G>T) has been reported. The most common clinical complications were growth retardation, renal involvement, mental motor retardation and developmental delay. Furthermore, one of our patients developed cardiomyopathy, another one died because of hepatic failure and one presented with lactic acidosis after linezolid exposure. Conclusion We have detected two novel mutations, including one splice-site mutation in the MUT gene and one frame shift mutation in the MMAA gene in 37 Turkish patients. We confirm the genotype-phenotype correlation in the study population according to the long-term complications.