A patient presents with a heliotrope rash, a malar rash and Gottron’s papules on the elbows and knees. She cannot comb her hair or climb the stairs due to muscle weakness. Lab results show an increased creatine kinase, positive antinuclear antibody (ANA) and anti-Jo-1 antibody. Biopsy reveals perimysial inflammation with perifascicular atrophy. She is treated with corticosteroids. What disease does the patient have?