Comparison of clinical and laboratory features and treatment responses in patients with clinically amyopathic juvenile dermatomyositis and classical juvenile dermatomyositis

The aim of this study was to compare the clinical and laboratory features, treatment choices and responses, and outcomes between patients with clinically amyopathic juvenile dermatomyositis (CAJDM) and classical juvenile dermatomyositis (JDM).We retrospectively reviewed the medical records of patients with CAJDM and JDM, and compared the 2 groups' clinical and laboratory data, treatment agents and responses, and outcomes.There were 38 JDM and 12 CAJDM patients, with female dominance. There was a higher delay time in diagnosis for CAJDM (P = 0.000). Compared to other clinical symptoms of JDM, muscle weakness and myalgia were more prominent in JDM than in CAJDM (P = 0.000). The absolute lymphocyte count was lower (P = 0.034) in patients with JDM than in those with CAJDM. Anti-p155/140 (TIF-1) antibody positivity was significantly more common in the CAJDM group (P = 0.000), while anti-NXP2 antibody was more common in the JDM group (P = 0.046). In terms of treatment, pulse corticosteroid usage was more common in patients with JDM than in those with CAJDM (P = 0.000).Close clinical follow-ups with effective treatments are important to prevent complications, such as calcinosis and skin ulcers, that may develop in patients with poorly controlled CAJDM. Anti-p155/140 antibodies may be a useful indicator for detecting amyopathic forms of dermatomyositis in children.