Objectives: To compare pulmonary function in patients with juvenile dermatomyositis (JDM) with that of matched controls; and to examine associations between pulmonary function impairment, high-resolution CT (HRCT) abnormalities and other disease variables in patients with JDM.
Methods: A total of 59 patients with JDM clinically examined a median 16.8 years (range 2-38 years) after disease onset were compared with 59 age-matched and sex-matched controls. Pulmonary function tests included spirometry, diffusing capacity for carbon monoxide (DLCO) and body plethysmography. In patients with JDM, HRCT scans were performed and cumulative organ damage and patient-reported health status assessed.
Results: Patients with JDM had lower total lung capacity (TLC) and DLCO compared to controls (p=0.003 and <0.001, respectively). A low TLC was found in 26% of patients versus 9% of controls (p=0.026), and a low DLCO in 49% of patients versus 9% of controls (p<0.001). HRCT abnormalities were found in 37% of patients, and included interstitial lung disease (ILD) (14%), chest wall calcinosis (14%) and airway disease (15%). Three patients were diagnosed as having ILD prior to the follow-up visit. A low TLC was more often found in patients with than without abnormal HRCT (50% vs 12%, p=0.002). HRCT abnormality correlated with cumulative organ damage (r(s)=0.346, p=0.008) and patient-reported health status at follow-up (p<0.005).
Conclusions: Patients with JDM had smaller lung volumes than controls; a restrictive ventilatory defect was found in 26% and HRCT abnormality in 37% of the patients, and these findings were associated. Although mostly subclinical, the relatively high frequency of pulmonary involvement highlights the systemic nature of JDM.