Clinical?Imaging?Pathological And Molecular Biological Features Of Mitochondrial Encephalomyopathy With Lactic Acidosis And Stroke-like Episodes

BackgroundMitochondrial myopathy with hyperlipidemia and stroke-like episodes are a group of syndromes that result from mitochondrial structure and dysfunction,oxidative phosphorylation disorder and adenosine triphosphate synthesis due to mitochondrial DNA or nuclear DNA mutations.Pavlakis first reported MELAS syndrome in 1984.The main manifestations included headache,epilepsy,stroke-like seizures,hirsutism,short stature,mental retardation,psychosis,vision loss,deafness,lactic acidosis,muscle intolerance fatigue and so on.This disease was relatively rare,and multiple mtDNA loci mutations could lead to this disease.The clinical manifestations of MELAS syndrome were complex,so easy to be misdiagnosed and poor prognosis.Therefore,early diagnosis and early treatment were very important.In recent years,cases of MELAS syndrome had been reported at home and abroad,but relatively little was reported about the clinical manifestations,imaging,muscular pathology,electron microscopy and molecular biology of MELAS syndrome.Data of36 patients with MELAS syndrome confirmed by the Fifth Affiliated Hospital of Zhengzhou University and the First Affiliated Hospital of Zhengzhou University were collected.Their clinical manifestations,neuroimaging,muscular pathology,electron microscopy and molecular biological features,and dynamic follow-up results were analyzed retrospectively.The purpose was to further strengthen the understanding of MELAS syndrome,and to provided reference for clinical diagnosis and treatment,and to reduce misdiagnosis.ObjectiveTo investigate the clinical manifestations,neuroimaging,muscular pathology,electron microscopic and molecular biological features of patients with mitochondrial myopathy with lactic acidosis and stroke like syndrome.MethodsData of 36 patients with MELAS syndrome diagnosed in the Fifth Affiliated Hospital of Zhengzhou University and the First Affiliated Hospital of Zhengzhou University from January 2012 to June 2017 were collected.Among them,30 cases underwent head CT scan,36 cases underwent T1WI,T2WI and FLAIR sequence,and30 cases underwent DWI and ADC sequence,28 cases underwent head MRA sequence,18 cases received enhanced MRI sequence,24 cases underwent ~1H-MRS sequence,and 11 cases underwent PWI sequence.Head magnetic resonance imaging was performed in 23 cases after 16 to 4 years.Pathological examination of muscle biopsy was performed in 33 cases.Hematoxylin eosin staining,modified Gomori trichrome,nicotinamide adenine dinucleotide,succinate dehydrogenase,cytochrome C oxidase,periodic acid schiff,oil red O and Sultan black B methods were used for histological staining.The microstructure of muscle cells was observed by transmission electron microscope in 15 cases.Gene sequencing was performed in 32patients and relatives.Among them,6 cases only extract peripheral blood for gene sequencing,and 26 cases were simultaneously collected peripheral blood and fresh urine was collected for gene sequencing.Firstly,4 common mutation sites,such as3243 A>G,3252 A>G,3271 T>C and 13513 G>A,were detected.If the result was negative,the whole sequence of mitochondrial DNA was sequenced.Result1.Clinical features The peak age of onset of MELAS syndrome was 6~13 years,and 13 patients had a positive family history.The main manifestations included epilepsy in 29 cases,stroke like episodes in 26 cases,headache in 15 cases,decreased visual acuity in 13 cases,intolerance fatigue 11 cases,hearing loss in 10 cases,short stature in10 cases,hairy in10 cases,fever in 8 cases,dementia in 7 cases,diabetes in6 cases,Vomiting in 6 cases,mental disorders in 5 cases,vomiting in 3 cases,muscle atrophy in 2 cases,bow in 2 cases,renal dysfunction in 2 cases,2 cases of diarrhea,intestinal obstruction in 1 case,extraocular muscle paralysis in 1 case and bed in 1case.14 patients had different incentives before stroke onset.Among them,there were 6 cases of upper respiratory tract infection,4 cases of fatigue,2 cases of drinking,1 cases of anti epileptic drugs,and 1 cases of emotional agitation.The serum lactate level was increased after the minimum exercise test.2.Imaging features 10 cases showed bilateral basal ganglia calcification symmetry in 30 patients who underwent head CT scan.In the acute phase of stroke attack,the head MRI mainly showed low signal intensity on T1WI,high signal intensity on T2WI and FLAIR,high or slightly higher signal intensity on DWI,high or slightly higher signal intensity on ADC.28 cases underwent head MRA,of which18 cases showed no obvious abnormalities,and 10 lesions showed cerebral vascular dilatation and branch enlargement.18 cases underwent head enhanced MRI,in which5 cases showed the sulci and gyri small punctate or linear enhancement,the remaining 13 cases had no obvious enhancement.In 24 cases of ~1H-MRS,the peak of N-aspartate peak was decreased significantly and the lactic acid peak was increased significantly in the acute phase.12 cases of cerebrospinal fluid in the lateral ventricle showed NAA peak was normal,and Lac peak was slightly increased,but Lac peak value was smaller than the lesion area.11 cases underwent head PWI sequence,and 9cases showed that the relative cerebral blood flow increased in the acute phase,which was high perfusion.The other 2 cases had normal rCBF.Acute lesions of the brain was swelling and shallow.In acute stage,the lesion showed laminar necrosis.Lesions could be scattered across the brain,and the distribution of dominant region did not conform to the blood vessels of the brain.The MRI examination of 23 patients revealed that the original lesions disappeared and were reversible,new lesions were appeared in other sites that showed they were wandering.There were 12 cases of softening foci,atrophy of brain and enlargement of ventricles after repeated attacks,which showed progressive.3.Myopathological features Pathological examination of muscle biopsy was performed in 33 cases.HE staining showed that the muscle fibers were different in size,and some of the muscle fibers were degenerated,necrotic and atrophic.18 cases of HE staining showed typical or atypical broken red fiber,and the cytoplasm of appeared basophilic granule deposition.A large number of ragged-red fibers(RRF)were found in 25 cases by modified Gomori staining.Typical or atypical ragged-red fibers were found in 26 cases by NADH staining,and the activity of oxidase was increased.Typical or atypical ragged-blue fibers(RBF)were found in 28 cases by SDH staining,and the activity of oxidase was increased.In 26 cases,the arterial walls of intermuscular arterioles were strongly SDH-reactive,that was SSV phenomenon,in which 2 cases had not seen ragged-blue fibers.The activity of oxidase was disappeared or decreased in 22 cases by COX staining,that was COX negative muscle fiber.But,the activity of oxidase was increased and decreased at the same time in 6 cases.18 cases were normal by PAS staining,and 15 cases of mild glycogen composition was increased.The lipid droplets was increased in 24 cases by ORO and SBB staining.15 patients were examined by electron microscopy,and the number and structural abnormalities of mitochondria were observed.Besides,the crystalline inclusion bodies in mitochondria were arranged in a"parking lot"pattern.4.Molecular biological characteristics Mt NDA mutations were found in all32 patients.22 patients had 3243 A>G mutation,16 patients of peripheral blood had3243 A>G mutation,and the mutation rate was 22.15%~100%,with an average of(35.82±11.26)%.20 cases of urine cells occurred 3243 A>G mutation,and the mutation rate was 38.46%~100%,with an average of(63.57±20.85)%.13 cases of the mothers or other relatives had the same 3243 A>G mutation site.13513 G>A mutation was found in 3 cases,and the 3302 A>G,1642 G>A,3271 T>C,3256 C>T,3093 C>G,3697 G>A and 15242 G>A mutations were found respectively in one case.Among them,3093 C>G,3697 G>A and 15242 G>A had been reported abroad,but there was no report in our country.No mutations were found in the fathers of all patients.Compared with the rate of mitochondrial DNA mutation in peripheral blood,the mutation rate of urine cells was significantly higher,and the difference was statistically significant(P<0.05).Conclusion1.Patients with MELAS syndrome were mainly adolescents.Epilepsy,stroke,and headache were the most frequent primary symptoms.Upper respiratory tract infection and fatigue were the most frequent predisposing factors for stroke like attacks.2.Cranial CT demonstrates symmetrical calcification of the basal ganglia and might be a characteristic of early changes in the MELAS syndrome.Acute lesions showed laminar necrosis.The most frequently involved parts of the lesion were occipital,temporal and parietal lobe,and the distribution of dominant region did not conform to the blood vessels of the brain.In the acute phase of stroke attack,the head MRI mainly showed low signal intensity on T1WI,high signal intensity on T2WI and FLAIR,high or slightly higher signal intensity on DWI,high or slightly higher signal intensity on ADC.Among them,FLAIR showed the focus of the lesions most clearly.Cranial ~1H-MRS showed a marked decrease of NAA peak and a significant increase of Lac peak in the lesion area.Cranial PWI showed a high perfusion status in the acute phase.3.RRF,SSV phenomenon and negative muscle fiber by COX staining were the main pathological changes of muscle in MELAS syndrome.SDH staining was the most sensitive method for RRF.SSV phenomenon could be the only pathological change of muscle in MELAS syndrome,which had diagnostic value.The inclusion of the crystalline inclusions in the mitochondria was a"parking lot"arrangement,which was a typical change in the electron microscope of MELAS syndrome.4.MELAS syndrome was maternally inherited,and it had heterogeneity and threshold effectgene.Gene sequencing was the gold standard for the diagnosis of MELAS syndrome.The 3243 A>G was the most common mutation site.5.The three mutations of 3093 C>G,3697 G>A and 15242 G>A in this research were reported for the first time in China,and some new phenotypes had been reported for the first time at home and abroad,which enriched the characteristics of mitochondrial gene mutation in MELAS syndrome.