Decreased aerobic capacity in children with juvenile dermatomyositis

Objective. To determine whether patients with juvenile dermatomyositis (DM) have limited aerobic capacity compared with healthy controls. Methods. Fourteen juvenile DM patients with inactive to moderately active, stable disease (age range 7-17 years) and 14 age- and sex-matched controls performed a maximal exercise test using a cycle ergometer. Oxygen uptake and power were measured at peak exercise (VO2peak and W-peak, respectively) and at anaerobic threshold (AT and W-AT). Juvenile DM disease activity and damage were also assessed. Results. Patients with juvenile DM had significantly reduced VO2peak (19.6 ml O-2/kg/minute in juvenile DM versus 31.1 ml O-2/kg/minute in controls), peak heart rate (166 versus 184 beats per minute), W-peak (1.6 versus 2.7 watts/kg), AT (11.1 versus 18.0 ml O-2/kg/minute) and W-AT (0.6 versus 1.4 watts/kg), compared to controls (P less than or equal to 0.05 for each). Aerobic exercise parameters correlated with physician global disease activity and damage, T1-weighted magnetic resonance imaging, and Childhood Myositis Assessment Scale scores (r(s) = 0.58 - 0.82, P less than or equal to 0.05). Conclusion. Patients with juvenile DM with a range of disease activity have a decreased aerobic and work capacity compared to healthy children. Aerobic exercise limitation in juvenile DM correlates best with measures of disease damage (global damage assessment, T1-weighted magnetic resonance imaging, and disease duration). Aerobic exercise testing may be valuable in the assessment of physical endurance, and aerobic training may be indicated as part of the therapeutic regimen in myositis patients with inactive to moderately active, stable disease.