Catching up with calcinosis: analysis of clinical characteristics, myositis-specific autoantibodies, and response to therapy in juvenile dermatomyositis.

OBJECTIVES: This study aims to evaluate the clinical, laboratory, and treatment profiles of juvenile dermatomyositis (JDM) patients with calcinosis. METHODS: A retrospective study was conducted at a tertiary-care referral centre in India (1992-2024), analysing JDM patients per modified Bohan and Peter criteria. Clinical data, myositis- specific autoantibody (MSA) profiles, and treatment details were compared between those with and without calcinosis. Calcinosis severity and treatment response were evaluated. Statistical analysis was performed using SPSS v. 29 software. RESULTS: Out of 157 JDM patients, 44 (28%) had calcinosis. These patients had a long diagnostic delay (12 months) and were more likely to be NXP2-positive (41%). Lipodystrophy was significantly associated with presence of calcinosis (39% vs. 5%). Severe calcinosis is linked to early age of onset of disease. Four children presented with calcinosis alone without clinically obvious skin or muscle disease, two of them were NXP2-positive. Patients with TIF1- gamma positivity predominantly had superficial calcinosis around large joints with skin ulceration, whereas NXP2 positivity had extensive and severe calcinosis. Among all patients with calcinosis, 39% improved while 61% had static/progressive disease. Analysis of drug response showed that the medications targeting calcium/phosphorus metabolism are linked to improvement in the calcinosis lesions over time. CONCLUSIONS: Calcinosis in JDM is associated with NXP2 autoantibody positivity and delayed diagnosis; however, severity correlates with early disease onset and specific MSA patterns. A subset of patients may present with calcinosis alone, underscoring diagnostic challenges. Drugs targeting calcium/phosphorus metabolism may be of benefit in reducing the severity of calcinosis in JDM.