Inflammatory myopathies belong to a heterogeneous group of acquired diseases involving the muscular system. The predominant symptom is weakness associated with muscle soreness. Polymyositis (PM) is a disorder that primarily affects adults and involves proximal muscle structures. Here, a case report of a 19-year-old patient diagnosed with PM is presented as confirmed by clinical evidence (involving proximal muscle, dysphagia), biochemical findings (elevated serum CK), high-resolution optical microscopy, and ultra structure and nuclear magnetic resonance of muscle. The patient was * Correspondencia: Wilson A. Bautista M. wbatu@hotmail.com Direccion postal: Servicio de Reumatologia, Hospital Militar Central Transversal 3 No. 49-00, Bogota, Colombia. Recibido: Octubre 27 de 2010 Aprobado: Diciembre 15 de 2010