Clinical, Imaging, Muscle Pathological And Molecular Genetics Features Of Pseudohypertrophy Muscular Dystrophy

BackgroundPseudohypertrophy muscular dystrophy is caused by a mutation in the gene encoding dystrophin,which causes destruction of cell membrane,intracellular creatine kinase(CK)leakage,and myocyte necrosis.In turn,adipose tissue and fibrous connective tissue proliferate,and a hereditary muscle disease that causes skeletal muscle atrophy occurs.The Dystrophin gene contains 79 exons,and exon point mutation,multiple or single exon deletions or repeated mutations will cause the disease.According to the different space structure and degree of function loss of dystrophin,muscle atrophy can be divided into Duchenne muscular dystrophy(DMD)with severe clinical symptoms and poor prognosis,and Becker muscular dystrophy(BMD)with mild symptoms and good prognosis.While the prognosis of DMD and BMD is very different,the two diseases are clinically almost indistinguishable only according to the clinical manifestations,which puzzles doctors in the clinical work.In recent years,with the continuous improvement of the treatment of pseudohypertrophy muscular dystrophy,the life expectancy of patients with DMD has increased from 20 years to 30 years old,which brings forwards high requirements for clinical work.Early diagnosis,timely treatment to improve their quality of life and extending life expectancy are imperative.At the same time,although powerful treatment can prolong the life span of DMD patients,the cured method has not been found.Therefore,avoiding the birth of fetal with DMD is still the most effective measure to avoid tragedy,which requires us to diagnose DMD children early and provide reasonable and effective genetic counseling and prenatal diagnosis guidance for their families.In recent years,cases of pseudohypertrophy muscular dystrophy have been reported at home and abroad,but there have been relatively few reports on the clinical manifestations,imaging,muscle pathology and molecular genetics of pseudohypertrophy muscular dystrophy.This study collected data from 40 patients with pseudohypertrophy muscular dystrophy diagnosed by the Fifth Affiliated Hospital of Zhengzhou University,then reviewed their clinical manifestations,muscle imaging,muscle pathology and molecular genetics features and explored the differences between patients with different age groups of DMD and BMD.This can help us further enrich the understanding of pseudo-hypertrophic muscular dystrophy,understand the development of DMD and BMD systematically,increase the early diagnostic rate and reduce missed diagnosis and misdiagnosis,which provide reference for clinical diagnosis and treatment as well as reasonable advice for the patients to have a good birth result.PurposesTo explore the difference and evolution of clinical manifestations,muscle imaging,muscle pathology and molecular genetics features of DMD and BMD patients with pseudohypertrophy muscular dystrophy,and to provide early diagnosis,disease evaluation and genetic counseling for the disease.MethodsData were collected from 40 patients diagnosed with pseudohypertrophy muscular dystrophy by the Department of Neurology,the Affiliated Hospital of Zhengzhou University from January 2013 to May 2018,which are separated into two DMD group and BMD group.According to the age,the DMD group is divided into two subgroups of DMD1 and DMD2.The age of onset,age of diagnosis,duration of illness,family history,first symptom,clinical manifestation,motor function scale score,serum enzyme,electrocardiogram,echocardiography,electromyography,muscle magnetic resonance and Mercuri score,skeletal muscle biopsy chemistry were collected.By comparing the results between the DMD group and the BMD group,and between the DMD1 and DMD2 subgroups,the differences of development between the two types of Pseudohypertrophy muscular dystrophy were discussed.Analyze gene sequencing results of 30 patients and their relatives,then discuss the regularity of dystrophin gene mutation and the relationship between mutation and clinical phenotype.Results1.Clinical manifestations: 40 patients were male,with an onset age of 4.4±1.8 years,31 patients with DMD had an onset age of 3.7±1.0 years,and 9 patients with BMD had an onset age of 6.9±1.9 years.Eight of them had a positive family history.Forty patients had muscle weakness at presentation,37 had lower limb weakness,17 had upper limb weakness,29 had muscle atrophy,25 had gastrocnemius hypertrophy,30 had Gower sign positive,and 2 had no walking.MFM scores were obtained in 40 patients.The BMD group scores were significantly higher than those in the DMD group,the DMD1 group scores were significantly higher than those in the DMD2 group,and MFM scores were negatively correlated with the duration of the disease.In 40 patients,creatine kinase,lactate dehydrogenase,alanine aminotransferase,creatine kinase isoenzyme and aspartate aminotransferase increased in different degrees,and the creatine kinase value gradually decreased with age and duration.Of the 40 patients,26 had abnormal ECG,and the abnormal rate of DMD group was higher than that of BMD group.9 of 20 had abnormal echocardiography,and 9 of 26 had elevated serum brain natriuretic peptide.Four patients with abnormal cardiac symptoms had echocardiography and BNP abnormalities besides abnormal electrocardiogram.All patients had myogenic damage by electromyography.2.Imaging: 40 patients underwent MRI of lower extremity skeletal muscle.37 cases were basically symmetrical on both sides,29 cases showed muscle atrophy,and there were two changes in muscle signal involved: high signal for T1 WI and T2 WI,SPAIR local the signal strength is increased.The skeletal muscle involvement of 40 patients was as follows: 40 patients with medial femoral and medial femoral muscle involvement,39 patients with rectus femoris and lateral femoral muscle involvement,36 patients with adductor muscle,35 patients with biceps femoris,semimembranosus 31 patients with semimembranosus,29 patients with long muscles,27 cases with semitendinosus,27 patients with sartorius muscle,and 26 patients with gracilis.Mercuri scores were scored in 40 patients with thigh skeletal muscle involvement,and the DMD group score was significantly higher than that of the BMD group,while the DMD2 group score was significantly higher than that of the DMD1 group.The Mercuri score in the DMD group was positively correlated with the duration of the disease,and negatively correlated with the MFM score and creatine kinase.And the Mercuri scores of the adductor muscle,the medial femoral muscle,the rectus femoris muscle,the lateral femoral muscle,the medial femoral muscle,and the biceps femoris were significantly increased,and the semimembranosus and semitendinosus scores were high,while the scores of the sartorius muscle,the gracilis and the longissimus muscles are low.3.Muscle pathology: 40 patients underwent muscle biopsy pathological examination.The muscle was investigated with histological examination,and under light microscopy,HE staining showed severe hyperplasia in the connective tissue of the fascia,and the muscle fibers were of different sizes.The muscle fibers with severe round atrophy were scattered or small,and the degeneration was visible.Necrosis,regenerative muscle fibers,and more opaque muscle fibers,a small amount of inflammatory cells infiltrated around the fascia and blood vessels.Modified Gomori staining did not show typical and atypical broken red fibers.NADH staining,SDH staining,and COX staining showed that the NADH dehydrogenase reaction,SDH,and COX enzyme activity were locally increased or decreased in some muscle fibers.PAS staining showed normal muscle glycogen components.As the disease progresses,ORO and SBB staining showed muscle fiber necrosis increases and fat components increase.Forty patients were anti-dystrophin-N,anti-dystrophin-C,anti-dystrophin-R monoclonal antibody immunohistochemical staining.The expression of dystrophin-N,dystrophin-C and dystrophin-R protein in the muscle fiber membrane of 31 patients with DMD significantly reduced or even was completely absent.The expression of dystrophin-N,dystrophin-C and dystrophin-R protein in the muscle fiber membrane of 7 patients decreased to a certain extent.One patient developed dystrophin-N deficiency,dystrophin-C and dystrophin-R decreased slightly,and another patient developed The dystrophin-R was absent,dystrophin-C,and dystrophin-N were mildly reduced.All 9 patients were diagnosed as BMD.The expression of dystrophin-N,dystrophin-C and dystrophin-R protein in muscle fiber membrane of 9 patients with BMD decreased to different degrees.There were significant differences in the expression of the control group,DMD group and BMD group.4.Molecular genetics: dystrophin gene mutation detection was performed in 30 patients,exon deletions were detected in 21 cases,exon duplicatians were detected in 3 cases,and point mutations were detected in 6 cases.Twenty-six mothers of patients with genetic mutations were tested and 21 were genetically altered carriers.No genetic mutations were found in fathers of all patients.There are two hotspot regions in the exon deletion mutation: one in the exon 4-16 region and the other in the exon 44-59 region.5.It is recommended to apply the “Diagnostic Flow Chart of Patients with Duchenne Muscular Dystrophy and Their Families” drawn in this study to conduct a standardized and efficient diagnosis of patients and their families.6.In this study,it was found that there was a hemizygous mutation in the region of 24 exon 36 of the patient,c.5081G>A,which was a nonsense mutation.This new mutation was reported neither in HGMD database nor in LOVD database.Conclusions1.In this study,it was found that pseudohypertrophy muscular dystrophy progressed gradually with age,and the type of disease,the dynamic evaluation of disease and the evaluation of patient prognosis can be judged by creatine kinase and MFM scores.Then,DMD heart involvement was more common and appeared earlier than BMD.Evaluation of cardiac involvement can be evaluated not only by electrocardiogram,but also by echocardiography and BNP results.2.Lower extremity magnetic resonance of pseudohypertrophy muscular dystrophy is characterized by bilateral lower limb symmetry muscle atrophy,fat infiltration,accompanied by inflammatory edema.MRI results showed that with age and disease progression,DMD muscle atrophy and fat infiltration gradually increased,while these of BMD were relatively mild.According to the Mercuri score,creatine kinase,MFM score,the severity of the patient's condition can be evaluated and muscle biopsy can be guided.Therefore,MRI can reflect the condition change and prognosis of the disease,and is easy to repeat,which is a non-invasive examination.3.On the basis of common chemical staining,the muscles still need to be immunohistochemically stained to find the reduction or absence of dystrophin to confirm the diagnosis,and to identify DMD and BMD.The results of this study showed that the degree of fibrotic necrosis,connective tissue hyperplasia and adipose tissue infiltration of DMD gradually increased with age and disease progression,while these of BMD were relatively mild.4.The Dystrophin gene is mutable and the region and size of the mutation are diversity.Large fragment deletions are the most common type of mutation,and the length of the gene mutation is independent of the type of disease.The combination of multiple ligation-dependent probe amplification technology,high-throughput sequencing technology,and Sanger method will develop an effective method for detecting dystrophin gene mutations.5.The “Diagnostic Flow Chart of Patients with Duchenne Muscular Dystrophy and Their Families” drawn in this study can lead to a standardized and efficient diagnosis of patients and their families.6.Our study found a new mutation,c.5081G>A,which enriched the dystrophin gene mutation map of patients with pseudohypertrophy muscular dystrophy.