Age-Related Differences Between Juvenile and Adult Autoimmune Inflammatory Myopathies.

Background: Clinical features and prognosis of autoimmune inflammatory myopathies (AIMs) can vary depending on the age of disease onset. The aim of this study was to compare the demographic characteristics, clinical features, laboratory findings, and long-term prognosis of juvenile and adult AIMs.

Methods: Patients diagnosed with AIM between 2009 and 2023 in the pediatric rheumatology and rheumatology departments of our hospital were included in this medical records review study. Demographic characteristics, clinical features, laboratory findings, treatments, and prognosis of juvenile and adult AIM patients were compared with statistical methods.

Results: Of the 94 patients diagnosed with AIM, 34 (36.2%) patients were juvenile and 60 (63.8%) patients were adult. At the time of diagnosis, while Gottron papules, dysphonia, and subcutaneous edema were more common in juvenile patients, fever was more common in adult patients (p = 0.003, p = 0.05, p = 0.005 p = 0.05, respectively). During follow-up, while calcinosis was more common in juvenile patients, lung involvement and malignancy were more common in adult patients (p = 0.022, p = 0.009, p = 0.006, respectively). The methylprednisolone pulse therapy requirement was significantly higher in juvenile patients (p = 0.0001). Clinically inactive disease was more common in juvenile patients (p = 0.01).

Conclusions: AIM with different onset ages is associated with distinct clinical manifestations and outcomes. The present study reported that in AIM patients, lung involvement and malignancy increase with age while clinically inactive disease decreases.