Paraneoplastic limbic encephalitis
Aug. 06, 2022
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There is a well-recognized association between cancer and myositis, mainly seen in classic dermatomyositis, amyopathic dermatomyositis, and immune-mediated necrotizing myopathy.
Idiopathic inflammatory myopathies, referred to as myositis, can be associated with cancer. Classic dermatomyositis, amyopathic dermatomyositis, and, to lesser extent, polymyositis are the most highly affected myositis phenotypes, whereas immune-mediated necrotizing myopathy has been linked to cancer as a paraneoplastic phenomenon. Cancer-associated myositis is defined as the concomitant presence of the 2 diseases within a 3-year period. However, a paraneoplastic patternthat is, when cancer abates, myositis disappears and when malignancy recurs, myositis returnsis not always observed.
• The myositis phenotype most often associated with cancer is dermatomyositis.
• The temporal criterion (cancer and myositis diagnosed within 3 years) is mandatory for the diagnosis of cancer-associated myositis.
• EUCLIDES (epidemiological useful clinical-laboratory-imaging development screening) is a proposed strategy for cancer screening in patients with myositis.
• The outcome of cancer-associated myositis depends more on the cancer than on the myositis.
• Close collaboration between the myositis-treating physician and oncologist is essential for optimal management of patients with cancer-associated myositis.
Idiopathic inflammatory myopathies, generally referred to as myositis, are a heterogenous group of diseases, systemic in nature and likely of autoimmune origin, characterized by an inflammatory infiltrate in muscle specimens (06). Five myositis phenotypes are currently recognized (25): dermatomyositis, which, when muscle symptoms are absent, is called amyopathic dermatomyositis; polymyositis, currently considered a rare condition and an exclusion diagnosis; necrotizing myopathy, which is mainly immune-mediated; sporadic inclusion body myositis; and overlap myositis, which includes the rare antisynthetase syndrome, manifesting as myositis, interstitial lung disease, and arthritis, among other features.
Myositis was first described in the late 19th century (32; 15) and its association with malignancy was reported some years later (13; 29; 15). In the first classification of inflammatory myopathies (03), the authors established the criteria for polymyositis and dermatomyositis and recognized that an association between cancer and myositis was clearly found in some patients, mainly those with dermatomyositis. Well-conducted epidemiological studies found that dermatomyositis is the myositis phenotype most often associated with cancer, with polymyositis involved to a lesser extent (28; 04; 11). Unfortunately, studies focused on other myositis phenotypes are scarce and often of poor quality. A few observational or cohort studies have reported a higher risk of cancer relative to the general population in patients with immune-mediated necrotizing myopathy, particularly those without autoantibodies, and a weaker association in those with antibodies against 3-hydroxy-3-methylglutaryl coenzyme A (anti-HMGCR) (02).
Current recommendations advocate taking into consideration the span of time between the 2 conditions to establish an association. A period of 3 years is now generally accepted; that is, cancer occurring within 3 years of the myositis diagnosis (31).
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