Pulmonary function and autoantibodies in a long-term follow-up of juvenile dermatomyositis patients

Objectives. Pulmonary disease is a rare complication in JDM, described in only a few studies. This long-term follow-up study aimed to (i) describe pulmonary involvement in a national cohort of JDM patients estimated by conventional spirometry, (ii) compare pulmonary impairment with overall JDM outcome, and (iii) identify possible associations between pulmonary impairment and myositis-specific autoantibodies (MSAs).Methods. Fifty-one JDM patients performed conventional spirometry in a cross-sectional follow-up study. The scores of the Myositis Damage Index (MDI), Myositis Damage by visual analogue scale (MYODAM-VAS) and physician's global damage assessment were used to estimate JDM outcome. ANAs, MSAs and myositis-associated autoantibodies were analysed in all patients.Results. Forty-two patients (82%) (mean follow-up time 14.3 years) had normal lung function. Four patients (8%) were diagnosed with JDM-related restrictive interstitial lung disease. No patients reported pulmonary symptoms. Patients with restrictive pulmonary function had increased long-term damage estimated by MDI (P = 0.008), MYODAM-VAS (P = 0.04), global assessment (P = 0.03) and number of organ systems involved (P = 0.009). We found significant correlation between the restrictive pulmonary function test and damage by the MDI (r = 0.43, P = 0.003), MYODAM-VAS (r = 0.44, P = 0.002), and global damage assessment (r = 0.43, P = 0.003). No association was found between the restrictive pulmonary function test and autoantibodies.Conclusion. In a long-term follow-up study of JDM patients, the majority of patients demonstrated normal lung function. However, restrictive pulmonary impairment was identified in 8% of patients, indicating a need for repetitive pulmonary follow-up in JDM patients. Restrictive pulmonary involvement was associated with increased long-term JDM damage.