OVERVIEW
Malignant tumor associated inflammatory myopathy (MTAIM) accounts for approximately 10% (6%-60%) of all idiopathic inflammatory myopathies. Patients with malignant tumors are often complicated by various myopathies, including inflammatory myopathies, such as polymyositis (PM), dermatomyositis (DM), and immune-mediated necrotizing myopathy (IMNM), etc. They are more common clinically, with more chances of occurring the older the patients are, and have certain pathomorphological changes with some It is more common in clinic, and the older the patients are, the higher the chance of occurrence.
Etiology
The etiology is unclear, and some people believe that inflammatory myopathy is a paraneoplastic syndrome, and its development may be related to the alteration of the immune status of the body, the existence of cross-reactive antigens between the tumor and the muscle, or the existence of potential viral infections in the muscle itself.
Symptoms
1. Patients may first have malignant tumor and later develop inflammatory myopathy, or malignant tumor occurs several years after the development of inflammatory myopathy, and occasionally the two lesions occur at the same time within 1 year and have a parallel course.
2. The main clinical manifestation is symmetrical muscle weakness, the pelvic girdle and scapular girdle muscles are most easily affected, and squatting, standing up and lifting up of both arms are difficult. When the neck muscles and pharyngeal muscles are involved, there may be weakness in raising the head, difficulty in swallowing, hoarseness and difficulty in voice formation. It may be accompanied by fever, myalgia, arthralgia, malaise, lack of appetite and weight loss.
3. Research suggests that ovarian cancer and gastric cancer are most often accompanied by inflammatory myopathy, which can also occur in other tumors, such as lung cancer, breast cancer, digestive tract tumor, hematological malignant tumor, thyroid cancer, nasopharyngeal carcinoma, renal carcinoma, etc. Tumor incidence is high in patients over 40 years old, especially in elderly patients over 60 years old.
Examination
Appropriate auxiliary examinations, such as blood routine, biochemistry, blood protein electrophoresis, carcinoembryonic antigen, immunological examination, urinary erythrocyte and cytological analysis, fecal occult blood, chest X-ray, sputum cytology, bone scan, ultrasound, etc. can be carried out to look for clues about the tumor. Gastrointestinal imaging, cervical scraping, histopathologic examination and other tests may be performed if necessary.
Diagnosis
Detailed history and comprehensive physical examination are very important for diagnosis, especially the examination of breast, pelvis and rectum should not be neglected.
Adult inflammatory myopathies with positive anti-nuclear matrix protein 2 (NXP-2) antibody are prone to malignant tumors, such as pancreatic cancer, gallbladder cancer, lung cancer, ovarian cancer and chronic lymphocytic leukemia.
Anti-NXP-2 antibody and anti-Transcription Intermediary Factor 1 (TIF-1)γ antibody had a higher positivity rate in patients with inflammatory myopathies associated with malignant tumors; the combination of anti-melanoma differentiation-associated gene 5 (MDA5) antibody and anti-TIF-1γ antibody was more meaningful in patients with tumor-associated dermatomyositis, especially those with clinically absent myopathic dermatomyositis (CADM); and the positive anti-small ubiquitin-like modification activating enzyme (SAE) antibody was negatively associated with malignant tumors. antibody positivity is negatively associated with malignancy; anti-3-hydroxy-3-methyl-coenzyme A reductase protein (HMGCR) antibodies are seen in paraneoplastic necrotizing myopathy. Among them, anti-TIF-1γ antibodies are not only of predictive value for malignancy-associated inflammatory myopathies, but are also important in the pathogenesis of the disease.
Treatment
Treatment of malignant tumors against the primary cause. The drug of choice for inflammatory myopathies is adrenal glucocorticoids. Prednisone dosage is appropriate to start large, according to the improvement of muscle symptoms, enzyme profile changes, adjust the hormone dosage, the drug should be effective in 3 weeks to 3 months. Generally need to take medication for 1 to 2 years. In severe cases, patients with unsatisfactory results of hormone therapy, in order to reduce the amount of hormone and side effects, can be combined with the use of immunosuppressants, such as azathioprine, methotrexate, cyclophosphamide. Immunomodulators, such as transfer factor, thymic peptide, intravenous immunoglobulin, etc.; plasma replacement can be done if necessary.