Benign acute childhood myositis following human parainfluenza virus type-1 infection.

Benign acute childhood myositis (BACM) is a post-respiratory tract infection condition of school-age children. Presentation is typically with acute onset calf pain and tenderness and refusal to walk or altered gait during the convalescent period of an influenza A or B infection. We describe a unique cluster of children with BACM following infection with human parainfluenza 1 virus, with no evidence of influenza A or B infection. BACM is a commonly missed diagnosis of altered gait in children presenting to the emergency department. This is the first report to describe a cluster of human parainfluenza virus type-1 associated BACM. We discuss the presentation, clinical examination and investigation results of the children identified. Furthermore, we review the current research surrounding BACM, overview the clinical presentation to healthcare professionals, and present an interesting case of a child presenting for the second time with BACM.