Polymyositis: is there anything left? A retrospective diagnostic review from a tertiary myositis centre.

The current classification criteria for idiopathic inflammatory myopathy (IIM) retain PM as a major disease subgroup. However, evolution in the understanding of IIM has suggested that many of these patients could be better described as having an alternative diagnosis. In the present study, we apply the latest understanding of IIM subtyping to retrospectively review PM diagnoses in a large cohort of IIM patients. Within a previously reported cohort of 255 patients from a UK tertiary myositis clinic, 37 patients classified as PM according to both the EULAR/ACR IIM criteria and expert opinion were identified. Clinical data and complementary tests were reviewed, and consensus decisions regarding final classification were reached in each case. Nine (9/37, 24.3%) patients remained classified as PM, 3.5% (9/255) of the original cohort; these PM patients were seronegative for myositis antibodies, responsive to immunosuppression, and in 4/7 (57.1%) patients where muscle biopsy was performed had HLA-1 upregulation and endomysial inflammatory infiltrates. Immune-mediated necrotizing myopathy (5/37, 13.5%) and connective tissue disease overlap myositis (7/37, 19%) were the main alternative diagnoses. The remaining patients were diagnosed as: unspecified myopathy (6/37, 16%), dermatomyositis (2/37, 5%), cancer-associated myopathy (3/37, 8.1%), and non-inflammatory myopathy (1/37, 3%, myofibrillar myopathy). Four patients (4/37, 10%) had insufficient data available to confidently reclassify. Our study confirms that PM can now be considered a rare IIM subgroup. A thorough examination, complete myositis autoantibody panel, and careful interpretation of the biopsy results is recommended to confirm the correct IIM sub-type.

Loarce-Martos J ，Lilleker JB ，Parker M ，McHugh N ，Chinoy H ... -  《-》

Polymyositis: an overdiagnosed entity.

van der Meulen MF ，Bronner IM ，Hoogendijk JE ，Burger H ，van Venrooij WJ ，Voskuyl AE ，Dinant HJ ，Linssen WH ，Wokke JH ，de Visser M ... -  《-》

Inflammatory Myopathies with Cutaneous Involvement: from Diagnosis to Therapy.

Dourmishev LA 《-》

Novel classification of idiopathic inflammatory myopathies based on overlap syndrome features and autoantibodies: analysis of 100 French Canadian patients.

Troyanov Y ，Targoff IN ，Tremblay JL ，Goulet JR ，Raymond Y ，Senécal JL ... -  《medicine》

Autoantibodies in adult patients with idiopathic inflammatory myopathies in Buenos Aires.

Gómez GN ，Gargiulo Mde L ，Pérez N ，Collado MV ，Suárez LV ，Khoury M ，Sarano JF ... -  《MEDICINA-BUENOS AIRES》