The Clinical Role Of Dysferlinopathy In Pathological Changes Of Necrotizing Myopathy And The Mechanism Of Dysferlin In Idiopathic Myositis

Background:Dysferlinopathy is an autosomal recessive skeletal muscle disease,which is caused by the mutation of the DYSF gene that causes the decrease or loss of dysferlin protein,and its clinical heterogeneity is significant.The typical pathological features of muscle biopsy are the enlargement of fiber diameter,connective tissue proliferation,muscle fiber necrosis and regeneration accompanying by decrease or loss of the expression of dysferlin protein in the myocutaneous membrane.Significant inflammatory cells infiltrated and scattered necrotic muscle fibers were found in Dysferlinopathy.At present,dysferlin functions mainly involve cell membrane repair and vesicle transport,but it can't explain inflammatory pathological features.In addition,we found that dysferlin was strongly positive in polymyositis(PM),dermatomyositis(DM)and immune-mediated necrotising myopathies(IMNM).Therefore,this study first we analyzed features of clinical manifestations,muscuoskeletal imaging and pathology in Dysferlinopathy with necrotizing myopathy.Then we investigated whether dysferlin participates in the pathophysiology of inflammatory myopathy.Material and methods:1.A total of 16 patients from the first affiliated hospital of Nan Chang university made diagnosis of dysferlinopathies through muscle biopsy and gene detection in between 2011 and 2017 were studied in our research.The clinical,imaging and pathological features of 5 Dysferlinopathies with simple necrotizing myopathy were analyzed.2.A total of 20 patients undergoing muscle biopsy from the first affiliated hospital of Nan Chang university between 2011 and 2017 were studied in our research,including 5 PM patients,5 DM patients,and 5 IMNM patients.Another 5 patients complained of muscle weakness,but those with normal muscle biopsy were normal controls.We made the examination of muscle specimens including conventional histological staining,enzyme histochemical staining,and immunohistochemical.We also analyzed the relation between the expression of dysferlin with MHC-1,NLRP3 and IL-1?.Results:1.5 Dysferlinopathy patients were 3 males and 2 females.The age of onset was 13-47 years old(average 26.8 years old).The course was 3 years of creatine kinase elevation to lower limb weakness.Three patients were asymptomatic,one patient had mild limb weakness and muscle soreness,and one patient only showed soreness in both lower extremities.Two patients had no deteriorationthrough telephone follow-up and no significant decreased in creatine kinase.One patient received oral hormonal therapy.After 10 months of reexamination,however,muscle MRI showed no significant reduction in muscle edema.Creatine kinase was elevated and strength of lower limb was descreased.2.Muscle pathology in 5 Dysferlinopathy patients showed scattered necrotic muscle fibers,including fresh and old necrosis.And inflammatory cells were infiltrated in old necrotic muscle fibers,predominantly CD68.A few inflammatory cells were seen around the individual intermuscular blood vessel in one patient.Dysferlin stain showed that the muscle fiber membrane and cytoplasm were negative.Two cases showed positive expression of MHC-1 in the cytoplasm of myofibrils and some myolemma.It could be seen that C5b-9 was deposited on necrotizing muscle fibers as well as part of non-necrotic muscle fibers,and in 1 case there was a bundle-like distribution of muscle fiber membranes.3.Dysferlin expression was significantly up-regulated in lesional muscle fibers of polymyositis,dermatomyositis,and immune-mediated necrotizing myopathy,and was statistically different from that of the control group(p<0.05).Polymyositis,also dermatomyositis,was statistically different from the immune-mediated necrotizing myopathy(p<0.05).The up-regulation of Dysferlin expression in cytoplasm was predominantly in early necrotic and regenerated myofibers,whereas in the three inflammatory myopathies,NLRP3 and IL-1? were mainly up-regulated in the cytoplasm of late necrotic/regenerated myofibers.Conclusions:1.Dysferlinopathy patients with pathological changes of necrotizing myopathy have a certain degree of clinical heterogeneity,but usually with mild symptoms,and early manifestations are similar to the clinical features of inflammatory myopathies,or asymptomatic high CK.The course of the disease is short,and MRI findings of muscle are mainly edema,mainly affecting the anterior thigh group and the posterior calf muscle.Hormonal therapy is ineffective and may even deteriorate.2.Dysferlinopathy with pathological changes of necrotizing myopathy are single myofibro necrosis and regeneration,with the abnormal expression and distribution of MHC-1 and the complement system.The pathological morphology of muscular dystrophy is not obvious,and it is easily misdiagnosed as necromyositis.Therefore,it is suggested that immunohistochemical staining of dysferlin should be routinely added to the pathological diagnosis of necrotizing myopathy.3.Dysferlin is involved in the inflammatory reaction of polymyositis,dermatomyositis,and immunonecrotic myopathy.The main role may be to inhibit overreaction of inflammation.The NLRP3 inflammasome and IL-1? mainly promotes disease progression.