Objective Heterogeneity exists among patients with myositis who have antinuclear matrix protein 2 (anti-NXP2) antibodies, although they usually present with severe muscle weakness. This study aimed to investigate the differences in phenotypes and prognoses among adult patients with myositis who have anti-NXP2 antibodies. Methods Adult patients with myositis who have anti-NXP2 antibodies were enrolled from January 2010 to December 2019. Their clinical features and laboratory data were recorded retrospectively. We followed up on their survival status until June 30, 2020. A hierarchical cluster analysis, Kaplan-Meier curves, and classification and regression trees were used to analyze the data. Results A total of 70 adult patients with myositis who have anti-NXP2 antibodies were enrolled. All patients experienced muscle weakness. A total of 11 patients did not present with rashes during disease progression, and 43 patients developed dysphagia. In total, 21 patients had interstitial lung disease (ILD), whereas no patients had rapidly progressive ILD. Hierarchical cluster analysis identified 2 clusters. Patients in cluster 1 were younger at disease onset, had a higher incidence of subcutaneous calcification, and had a lower incidence of V sign and shawl sign. Patients in cluster 2 had a higher frequency of ILD, accompanied by lower levels of lymphocytes and higher levels of serum ferritin. Moreover, patients in cluster 2 had worse prognoses. Conclusion Patients with myositis who have anti-NXP2 antibodies may present with different phenotypes that are characterized by unique features and prognoses.

ObjectiveThe clinical features of myositis specific antibody negative dermatomyositis (MSA negative DM) varied greatly, and there were few reports in the literatures. This study aimed to describe and expand the clinical phenotypes and prognoses of MSA negative DM patients.Methods MSA negative DM patients were identified from January 2010 to June 2020. We retrospectively reviewed the clinical features and laboratory data. The survival status was followed up until July 31. 2020 SPSS version 21.0 and R version 3.6.1 software were used for the statistical analyses. ResultsA total of 97 MSA negative DM patients were enrolled. The most common type of rashes was heliotrope rash (80.4%). More than half of the patients (55.7%) had interstitial lung disease (ILD), and seven of them developed rapid progressive ILD. There were eleven patients with tumours. During the follow-up, twelve patients died, of whom 5 (41.7%) died due to infection. Two phenotypes of MSA negative DM patients were identified by cluster analysis. Patients in cluster 1 developed muscle weakness, mechanic's hands, arthritis, and ILD more frequently. Patients in cluster 2 had a higher incidence of heliotrope rashes. Patients in cluster 1 tended to have worse prognoses, wherein the 1-year and 5-year survival rates (81.1% and 78.4%, respectively) were lower than those in cluster 2 (97.6% and 95.2%, respectively), with p-value 0.04 and 0.056, respectively. ConclusionThrough cluster analysis, different clinical phenotypes of MSA negative DM patients were determined. The prognoses of the two subgroups were different in terms of survival rate and cause of death.

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