Amyopathic and anti-TIF1 gamma-positive dermatomyositis: analysis of a monocentric cohort and proposal to update diagnostic criteria

Background Dermatomyositis (DM) is a group of autoimmune diseases characterized by a variable degree of skin symptoms and myopathy. An amyopathic form of DM (ADM) has been described, and more recently, an anti-TIF-1 gamma-positive subtype, characterized by poikiloderma and associated with a relatively high risk of cancer. Objectives To characterise a cohort of DM patients. Material and Methods A cohort of 29 DM patients was followed between January 2004 and March 2019, and investigated for clinical characteristics, pathological features based on electromyography and MRI, laboratory data, and auto-antibody profile. Results Based on the investigations, DM was shown to be heterogeneous. However, we identified a subgroup of anti-TIF-1 gamma-positive patients who all shared heliotrope erythema. Furthermore, we observed a positive correlation between serum glutamicoxaloacetic transaminase (GOT) and creatine kinase (CK) concentrations in patients with anti-TIF-1 gamma antibodies, which is not found in patients with anti-MDA-5 antibodies. Conclusion Based on the findings of this study, we propose an update of the Sontheimer et al. diagnostic criteria to improve the sensitivity of diagnosis for ADM. In addition, we describe a significant association between serum GOT and CK levels in DM patients with anti-TIF-1 gamma antibodies, and further highlight the significance of heliotrope rash as a clinical hallmark for this particular subset of patients.