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Rheumatology needs to move away from ‘old terminology’ in diagnosing myositis syndromes as simply ‘polymyositis’ and characterise the disease much better, the Irish Society for Rheumatology 2025 Spring Meeting was told.
A noted international expert on myositis, Dr Harsha Gunawardena, Consultant Rheumatologist, Autoimmune CTDs and Vasculitis, Divisional Clinical Director, Neurosciences Musculoskeletal Division, North Bristol NHS Trust, UK, gave a detailed presentation on diagnosis and management approaches at the meeting.
Dr Gunawardena’s PhD on myositis syndromes phenotypes was the first to describe several novel autoantibody markers. He has published on myositis overlap syndromes, autoantibodies, CTD-ILD reviews and guidelines and is a lead member of UK Myositis Network, Myositis UK patient charity scientific committee, and the British Society of Rheumatology myositis guidelines group.
He began his talk by emphasising that idiopathic inflammatory myopathies have a wide spectrum of disease. While there are shared features – myopathy, skin rashes, systemic/constitutional upset – “no one patient is necessarily the same”.
Presentations of the disease can differ: Some patients have severe muscle involvement at onset; others exhibit no clinical myositis (amyopathic); some are at higher risk of lung disease, while others have pronounced skin manifestations, including ulceration or calcinosis. In certain cases, inflammatory arthritis or gastrointestinal involvement predominates, and in others, there is an association with cancer.
Discussing clinical presentation, he stressed the importance of getting the basics right – key measurements include neck flexion, shoulder abduction, and hip extension.
Dr Gunawardena noted that there are different degrees and patterns of muscle weakness, which are very important to assess and clarify. “Facial weakness makes me think, for example, that they might have something else going on, while if it is predominantly forearm and not limb it may be a differential diagnosis.”
Discussing the role of neurophysiology in diagnosis, Dr Gunawardena noted that he finds it particularly helpful when considering differential diagnoses – for example, when questioning whether a condition might be a mimic or whether there is an additional cause for a patient’s weakness.
“That is where EMG and nerve conduction studies can be really, really helpful,” he explained, “because you get different patterns if it is a non-inflammatory muscle disorder, or if there is a predominant neuropathy which drives the denervation of muscle.”
Regarding the use of MRI, Dr Gunawardena said while he finds it “very useful at baseline”, and for surveillance, particularly when the cause of the flare is unclear, interpretation can be an issue.
“High signal (myo-oedema) does not necessarily mean ‘myositis’, it simply means it is an abnormal finding…. It is not diagnostic.”
He advised always correlating findings with T1-weighted images and assessing the degree of atrophy.
Antibody testing in myositis is an area that has evolved significantly in recent years.
Dr Gunawardena said this “is great and gives us a lot more information, but the problem is they are not overly reliable, so they are not the be-all and end-all”.
“If your lab does immunofluorescence, that is really helpful as it gives you a pattern, which indicates what the target antigen is.”
A key focus of Dr Gunawardena’s talk was the requirement for muscle and skin biopsy, which is a somewhat controversial issue in diagnosing myositis syndromes.
“I’m doing those an awful lot less than I used to, as there is a lot more information from the other tests.”
Specifically, in relation to patients with features that fit with clinico-serological phenotype, he said he believes a biopsy is not needed, while in patients with classic immune-mediated necrotising myopathy and positive antibodies, he is doing fewer biopsies.
On the other hand, in patients with clinical features of proximal myopathy who are seronegative and those with unusual patterns of weakness not responding to treatment, Dr Gunawardena said a biopsy should be done. “Ultimately, I still biopsy patients who have an undefined myopathy.”
“Another tip – we can overdiagnose myositis. A raised CK and muscle weakness does not always mean myositis. Think about the atypical features in that situation.”
A raised CK and muscle weakness does not always mean myositis
Dr Gunawardena emphasised the importance of trying to define the syndrome to guide tests, and predict complications and treatment strategies, and to avoid using ‘polymyositis’ as a diagnostic term.
Furthermore, he advised meeting attendees that they should always reconsider when presented with refractory polymyositis. “This is one of the most common referrals to my clinic, and these patients have been given every immunosuppressive under the sun, but are not getting better. I stop, and I pause, and I say to the patient that I suspect they have something else, as inflammatory markers generally respond to treatment.”
Dr Gunawardena then moved on to discussing the management of the different myositis syndromes, using a number of clinical case study examples. He stressed the importance of multi-disciplinary collaboration, particularly with complicated cases.
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