Juvenile dermatomyositis (JDM) has a wide spectrum of clinical presentations. In the last decade, several
myositis-specific
antibodies have been identified in patients with JDM and connected with specific organ involvement or specific clinical picture. It has been published that the presence of anti-NXP2
autoantibodies presents a risk for
calcinosis in patients with JDM. We aimed to investigate the prevalence of
calcinosis and response to the treatment in JDM patients with anti-NXP2. In a retrospective, multinational, multicenter study, data on 26 JDM (19 F, 7 M) patients with positive anti-NXP2 were collected. The mean age at disease presentation was 6.5 years (SD 3.7), the median diagnosis delay was 4 months (range 0.5-27 months). Patients were divided into two groups (A and B) based on the presence of
calcinosis, which occurred in 42% of anti-NXP2 positive JDM patients (group A). Four patients already had
calcinosis at presentation, one developed
calcinosis after 4 months, and 6 developed
calcinosis later in the disease course (median 2 years, range 0.8-7.8). The differences in laboratory results were not statistically significant between the groups. The mean age at disease presentation (5.2/7.5 years) trended toward being younger in group A. Children with
calcinosis were treated with several combinations of drugs. In four cases,
rituximab and, in one case, anti-
TNF alpha agents were used successfully. Disease outcome (by evaluation of the treating physician) was excellent in four, good in two, stable in two, and poor in three patients. None of the patients from group B had a poor disease outcome. In conclusion, JDM patients with anti-NXP2 are prone to develop
calcinosis, especially if they present with the disease early, before 5 years of age. The development of
calcinosis is associated with worse disease outcomes. The combination of several
immunomodulatory drugs and biologic drugs can stop
calcinosis progression; however, there are no evidence-based
therapies for treating
calcinosis in JDM patients.