| Objective:The purpose of this study was to analyze the clinical features,laboratory tests,imaging features,and pathological characteristics of patients with immune-mediated necrotizing myopathy who were positive for anti-signal recognition particle antibodies;to investigate the factors influencing their poor prognosis,and to provide a basis for the clinical diagnosis and treatment and prognostic assessment of this disease.Methods:Fifty-five patients diagnosed with immune-mediated necrotizing myopathy positive for anti-signal recognition particle antibodies in the Department of Neurology,First Hospital of Jilin University from January 2017 to December 2022 were screened for inclusion in the study,and clinical data such as age of onset,gender,disease duration,clinical symptoms,serological tests,muscle electrophysiology,muscle NMR of both lower limbs,and muscle pathology tissue biopsy were retrospectively analyzed to summarize the characteristics of the patients.The patients were followed up at 12 months after diagnosis,and the modified Rankin Scale(m RS)score was used as a criterion for short-term prognosis.m RS score ≤2 indicated good prognosis and >2indicated poor prognosis.55 patients were divided into two groups with good prognosis and poor prognosis based on m RS score.The influencing factors were analyzed for correlation.SPSS 25.0 statistical software was used for statistical analysis,and the mean ±standard deviation was used for normally distributed measures,and the t-test was used for comparison between groups;the median and interquartile range were used for skewed measures,and the rank sum test was used for comparison between groups;theχ2 test or Fisher’s exact probability method was used for comparison of count data;the multi-factor logistic regression analysis was used for short-term prognostic impact factor analysis,and ROC curves were constructed.The test level of α=0.05 was used,and P<0.05 was considered a statistically significant difference.Result:A total of 55 patients with immune-mediated necrotizing myopathy(SRP-IMNM)positive for anti-signal recognition particle antibodies were included in this study,of which 14 were male and 41(74.5%)were female,with a male to female ratio of1:2.92.The total sample age at onset ranged from 22-73 years,with a mean age at onset of(52.18±12.11)years.The duration of the disease ranged from 0.5-36 months,with a mean of(5.29 ± 6.46)months.Myasthenia(72.7%),myalgia(58.2%)and myalgia(63.6%)were the most common clinical manifestations,followed by dysphagia(29.1%),dysarthria(21.8%),and rash(12.7%),and women were more likely to have symptoms of myasthenia(P < 0.05)and myalgia(P < 0.048)than men.Creatine kinase(CK)was elevated in 54 of 55 patients(98.2%),and the mean level of CK was 3958.51 ± 2698.52 U/L.Patients with poor prognosis had elevated CK,creatine kinase isoenzyme(CK-MB),aspartate aminotransferase(AST),glutamate aminotransferase(ALT),C-reactive protein(CRP),erythrocyte sedimentation rate(ESR),and low-density lipoprotein(LDL)were higher than those of patients with good prognosis,but the difference of CK between groups with different prognosis was not statistically significant,which was considered to be related to the serious destruction of muscle fibers in patients with longer disease duration,and CK was no longer significantly elevated.3.Among the 30 patients who completed thigh muscle nuclear magnetic(MRI),fatty infiltration was present in 90.0% of the thigh muscles,suggesting extensive fatty infiltration in patients with SRP-IMNM and severe involvement of the posterior thigh muscle group;93.3% of the patients had inflammatory edema in the thigh muscles,which was more diffuse,and their infiltration pattern had no obvious characteristics.4.Massive myofiber necrosis and regeneration are typical pathological features of SRP-IMNM,and are mostly accompanied by a small amount of inflammatory cell infiltration.Positive expression of MHC-I molecules in non-necrotic myofibers was seen in most patients,and macrophages and CD4+ T cells were the main inflammatory cell components.The CD8 positivity rate was higher in the poor prognosis group than in the good prognosis group,and the difference between groups was statistically significant(P < 0.05).5.The results of univariate analysis showed that dysphagia,myasthenia,combined interstitial lung disease,combined connective tissue disease,ALT,and CD8 positivity were closely related to poor prognosis,and when the above indicators were included in the multifactorial analysis,the results showed that positive expression of inflammatory cells CD8 in dysphagia,myasthenia,combined connective tissue disease,and skeletal muscle pathology were independent risk factors for poor prognosis.The positive expression of inflammatory cells CD8 as an independent risk factor for poor prognosis suggested the possible involvement of T cells in the pathogenesis.Conclusion:(1)Patients with SRP-IMNM tend to start around the age of 50,more women than men,and the duration of the disease varies.(2)The most common clinical symptoms of SRP-IMNM are muscle weakness and myalgia in the proximal extremities,and they are more likely to occur in women than in men.(3)CK is significantly elevated in patients with SRP-IMNM,often >3000 U/L,which does not fully reflect the severity of the disease.(4)Patients with SRP-IMNM have extensive muscle fat infiltration,with the posterior thigh muscle group being the most important;the inflammatory edema is diffuse and the infiltration pattern is not characteristic.(5)The pathology of patients with SRP-IMNM is characterized by massive myofiber necrosis and regeneration,with fewer inflammatory cells.(6)Dysphagia,myasthenia,combined interstitial lung disease,combined connective tissue disease,ALT,and CD8 positivity were closely related to poor prognosis,with positive expression of inflammatory cells CD8 in dysphagia,myasthenia,combined connective tissue disease,and skeletal muscle pathology as independent risk factors for short-term poor prognosis in patients with SRP-IMNM. |
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