Clinical, Molecular Pathological And Genetic Study Of Chinese Patients With Congenital Muscular Dystrophy

Background: Congenital muscular dystrophy(CMD) is a kind of complex neuromuscular disorders,which is primary and progressive.Typically patients with CMD present at birth or in the neonatal period with severe muscular weakness,hypotonia, joint contracture and hyporeflexia or tendon reflex disappear.At the same time,elevated serum creatine kinase(CK) levels and muscle source damage in electromyogram(EMG) can be seen.Muscle biopsy histopathology analyze shows myodystrophia changes,including variability in fiber size, dysplastic muscle fibers with small and round fibers,connective tissue proliferation,normal distribution of distropin and no obviously special changes of ultramicrostructure of muscle fibers.Now CMD can be classified into 3 major groups at abroad(Table 1-1).CMDs lead to mutilation and lethality at high rate,bring heavy burden to family and society.Now this kind of diseases can be diagnosed majorly by clinical features and to definite according to muscle biopsy.There are only some CMD clinical case reports in our country and deficiency of molecular pathological and genetic data. Objective: To carry out phenotype analyze, molecular pathological and genetic study in 15 CMD patients which were collected in Peking University First Hospital,to comprehend the clinical features of part types of CMDs in our country,establish diagnostic method of some types of CMDs and provide evidence of genetic counseling and prenatal diagnosis for these types of CMDs.Methods: To analyze and summarize patients'information,including the clinical features,serum CK levels,EMG and cranial MRI characteristics in 15 CMD patients which were collected in Peking University First Hospital,to divide all the patients into two groups:congenital muscular dystrophy type 1A(12 cases) and muscle-eye-brain disease(3 cases).Some patients received muscle biopsy and routine pathological checks and immunohistochemistry staining was perfomed on biopsied muscle speciments with anti-lamininα2(merosin) antibodies,antiα-dystroglycan(α-DG),antiβ-dystroglycan(β-DG) and anti C-terminal of dystrophin(Dys-C) antibodies.Informed consent was obtained from all the muscle-eye-brain disease families tested. Genomic DNA was extracted using standard procedures from the peripheral blood. PCR assays were performed to detect all the virulence genes of muscle-eye-brain disease:POMGnT1,FKRP,FCMD, POMT2.DNA sequence analysis were used to find gene mutations.These data were collected from Peking University First Hosipital and these works were all finished in pediatrics lab and neuropathologic lab of Peking University First Hosipital.Results:1. 6 congenital muscular dystrophy type 1A patients in 12 received muscle biopsy.They had common clinical features:onset at birth or in 4 monthes,motor development milestone delayed,striking joint contracture,muscle weakness,hypotonia,hyporeflexia or tendon reflex disappear.Common auxiliary examination results:serum CK levels increased by 10~50 times,EMG showed muscle source damage, cranial MRI showed abnormal signal in the white matter. Routine pathological checks of skeletal muscle speciments from these patients showed typical characteristics of CMD.Special immunohistochemistry staining showed merosin-stain negative,α-DG,β-DG and Dys-C-stain positive.Although Other 6 patients lacked pathology data,they had the similar clinical features and auxiliary examination results.2. 2 muscle-eye-brain disease patients in 3 received muscle biopsy.These 2 patients have common clinical features:onset at birth or in 1 monthes,mental retardation,motor development milestone delayed and muscular dystrophy characteristics,containing muscle weakness,hypotonia, triking joint contracture,hyporeflexia or tendon reflex disappear.Common auxiliary examination results:serum CK levels significant increased,EMG showed muscle source damage.They all had characteristical appearances:ocular abnormalities and brain malformations,including weak visual fixation, light reaction torpidity,optic nerve atrophy and cranial MRI showed multi-bursula focus of cerebellum and dysplastic brainstem. Routine pathological checks of skeletal muscle speciments from these 2 patients showed typical characteristics of CMD.Special immunohistochemistry staining showedα-DG-stain negative,merosin,β-DG,Dys-C-stain positive,indicated hypoglycosylation ofα-DG,which supported the diagnosis ofα-dystroglycanopathy. Although Other 1 patient lacked pathology data,he had the similar clinical features and auxiliary examination results.Gene mutation analyze were used in all 3 patients.By screening all the virulence genes of muscle-eye-brain disease:POMGnT1,FKRP,FCMD,POMT2,we found 31 single nucleotide polymorphisms (SNPs),5 samesense mutation.We did not find pathogenic mutation in coding regions of these 4 genes. Conclusions: This is the first report to diagnosis 6 congenital muscular dystrophy type 1A patients and 2α-dystroglycanopathy patients clinically and molecular pathologically in China,in which we defined the clinical features of congenital muscular dystrophy type 1A in our country. This is the first time to establish diagnostic method of part types of CMDs in clinic,molecular pathology and genetics.