A prospective natural history study of inclusion body myositis: Implications for clinical trials

Eleven patients with untreated inclusion body myositis (IBM) were prospecti vely studied during a 6-month period that included muscle strength, lean bo dy mass, and muscle mass measurements. There was an overall quantifiable me an decline in percent of predicted normal muscle strength of 4% from baseli ne in a 6-month period, but one third of patients showed no change or sligh t improvements in strength. Short-term treatment trials in IBM will require large numbers of patients to detect slowing, arrest, or even slight improv ement in muscle strength.