Sporadic inclusion body myositis (sIBM) is a rare idiopathic inflammatory myopathy characterized by chronic proximal leg and distal arm asymmetric muscle weakness. Its prevalence is estimated between 10 and 100 cases per million, over the age of 50. Little is known about the natural course of the disease, the delay between onset and diagnosis, the patterns of disease management and treatment in routine practice, as well as the burden for patients.