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Purpose of review Necrotizing myopathy is a broad term. It includes patients with the recently described immune-mediated necrotizing myopathies (IMNM) who have specific antibodies, such as anti-hydroxy-3-methylglutaryl-CoA reductase or anti-signal recognition particle, seronegative phenotypes that can be associated with cancer, and other types of myositis and connective tissue diseases involving necrotic muscle fibers as a characteristic pathologic feature. Necrotizing myopathies that are not immune-mediated, such as those caused by drugs, dystrophies, infections, or even hypothyroidism are also included. The purpose of this review is to address the differential diagnosis of these disorders. Recent findings New IMNM have been described over the last few years, some of them related with checkpoint inhibitors, drugs that are being increasingly used in cancer treatment. Necrotizing myopathy has also been reported in association with specific phenotypes and autoantibodies (e.g. anti-Mi2 dermatomyositis, antisynthetase syndrome, and myositis associated with antimitochondrial antibodies). Rarer cases associated with graft-versus-host disease and severe acute respiratory syndrome coronavirus 2 infection are also emerging. Summary Differentiation between patients with IMNM and those without the superimposed autoimmune phenomena helps clinicians determine the best individualized approach to use and the appropriate immunosuppressive therapy, whenever needed.

Necrotizing myopathy is a broad term. It includes patients with the recently described immune-mediated necrotizing myopathies (IMNM) who have specific antibodies, such as anti-hydroxy-3-methylglutaryl-CoA reductase or anti-signal recognition particle, seronegative phenotypes that can be associated with cancer, and other types of myositis and connective tissue diseases involving necrotic muscle fibers as a characteristic pathologic feature. Necrotizing myopathies that are not immune-mediated, such as those caused by drugs, dystrophies, infections, or even hypothyroidism are also included. The purpose of this review is to address the differential diagnosis of these disorders.New IMNM have been described over the last few years, some of them related with checkpoint inhibitors, drugs that are being increasingly used in cancer treatment. Necrotizing myopathy has also been reported in association with specific phenotypes and autoantibodies (e.g. anti-Mi2 dermatomyositis, antisynthetase syndrome, and myositis associated with antimitochondrial antibodies). Rarer cases associated with graft-versus-host disease and severe acute respiratory syndrome coronavirus 2 infection are also emerging.Differentiation between patients with IMNM and those without the superimposed autoimmune phenomena helps clinicians determine the best individualized approach to use and the appropriate immunosuppressive therapy, whenever needed.

Despite the well-recognized association between malignancy and myositis, definite data indicating the best strategy for diagnosing cancer in myositis patients is lacking. In this article, we review the data on cancer screening in patients with myositis, and propose an algorithm for this purpose based on recently published data.Evidence has recently emerged supporting blind screening in patients with certain myositis phenotypes. In addition to the clinical examination, imaging techniques such as PET/computed tomography scanning and whole-body MRI, and determination of the autoantibody profile beyond anti-TIF1γ antibody, the well known cancer biomarker in dermatomyositis, will help the clinician face this complex clinical situation. Molecules related to the checkpoint inhibitor pathway, specifically soluble programmed death 1, may also have a role in the diagnostic work-up of cancer in myositis. In the future, blood tests analysing circulating DNA will certainly help in detecting patients with cancer-associated myositis (CAM).A step forward has been achieved in the pathway to establish optimal cancer screening for myositis patients. International consensus guidelines for an effective diagnostic work-up of CAM are in progress and will be of paramount importance to improving the outcome in these patients.

Purpose of review Currently available data support the idea that inflammatory myopathies, particularly dermatomyositis, are paraneoplastic diseases. Cancer screening is usually recommended in patients with these conditions, but there is no consensus regarding how and how often screening should be performed. This review will address recent advances in our understanding of the relationship between cancer and myositis and describe new data regarding the best approach for cancer screening in myositis patients. Recent findings A newly described autoantibody to a 155-kDa nuclear protein, identified as transcription intermediary factor 1-gamma (TIF1-γ), has proven useful for cancer screening in patients with dermatomyositis. Occult tumor detection by PET/computed tomography (PET/CT) seems to be a good alternative to broad conventional screening. A combination of both methods, detection of autoantibodies against p155 and PET/CT study, may be the best approach to ascertain the presence of occult malignancy in patients with dermatomyositis. Summary Advances in immunology and imaging techniques are increasing the accuracy of occult malignant cancer detection in dermatomyositis patients. Nevertheless, the diagnosis of cancer in this population remains elusive in some cases. Further investigation is needed to improve our knowledge of the link between myositis and cancer.

PURPOSE OF REVIEW: Biological agents are therapies designed to target a specific molecular component of the immune system, and are currently licensed for use in autoimmune rheumatic, digestive, dermatological and systemic diseases. However, their use has been linked with the paradoxical development of autoimmune processes. RECENT FINDINGS: More than 1500 cases of autoimmune diseases induced by biologics have been reported, including a wide variety of both systemic (lupus, vasculitis, sarcoidosis, antiphospholipid syndrome and inflammatory myopathies) and organ-specific (interstitial lung disease, uveitis, optic neuritis, peripheral neuropathies, multiple sclerosis, psoriasis, inflammatory bowel disease and autoimmune hepatitis) autoimmune processes. Although these processes are overwhelmingly associated with anti-TNF agents, recent cases have been associated with therapies directed against other cytokines, B or T-cells, illustrating that even though targeting a particular immune molecule may be associated with an excellent clinical response in most patients, an unexpected autoimmune response may arise in some cases. SUMMARY: As the use of biological therapies expands, the number and diversity of induced autoimmune disorders should be expected to increase. Paradoxically, for many of these drug-related processes, current treatment indications include the very biological agent producing the adverse event.