Here we report two patients with severe juvenile dermatomyositis (JDM) complicated with extra musculocutaneous involvement. The first case (a 10-year-old boy) had unusual initial presentation of JDM complicated with interstitial lung disease documented with high-resolution computed tomography. He had a rapidly progressive course and died in 7 weeks after the onset of the disease despite steroid and immunosuppressive treatment. The second case (a 14-year-old boy) was presented with myositis complicated with hepatitis. He also had a chronic course of JDM with unfavorable outcome. It appears that the prognosis of patients with severe JDM is related with the degree of autoimmune vasculitis on extra musculocutaneous involvement.