Clinical characteristics and long-term prognosis of anti-MDA5-positive dermatomyositis: a comparative study across age groups

OBJECTIVES: Research focused on clinical differences and long-term prognosis in anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis (anti-MDA5+ DM) patients across age groups remains limited. This study aimed to explore the differences in the clinical manifestations and long-term mortality of anti-MDA5+ DM patients across age groups. METHODS: We included 318 newly diagnosed anti-MDA5+ DM patients, recruited from June 2018 to January 2024. The median follow-up time was 22.5 months (4.5-36 months). The Cochran-Armitage test for trend (CATT) was employed to assess the statistical significance of changes in the proportion of clinical characteristics across different age groups. Cox regression analysis and a nomogram model were developed to stratify the risk associated with mortality. RESULTS: In the cohort of 318 patients, 123 (38.7%) were aged < 50 years, 124 (39.0%) were aged 50-59 years, and 71 (22.3%) were aged ≥ 60 years. Clinical manifestations and comorbidities such as cough, Pneumocystis jirovecii pneumonia (PJP), dyspnea, and rapidly progressive interstitial lung disease (RP-ILD) increased with age, while rash and arthralgia decreased. PJP was a major factor in poor prognosis, especially among older patients who were more susceptible to infection. The nomogram, the first prognostic model incorporating both age and PJP infection in anti-MDA5+ DM, demonstrated its independent and combined effects on mortality and enabled early risk stratification, providing a valuable tool for clinical decision-making. CONCLUSIONS: Clinical manifestations and laboratory parameters varied in anti-MDA5+ DM patients across different age groups. Advanced age and PJP are major factors associated with poor prognosis, with patients aged ≥ 60 years showing the highest mortality and being predominat in the high-risk group.