Inclusion body myositis: an underdiagnosed myopathy of older people.

Inclusion body myositis (IBM), a condition characterised by progressive muscle weakness and inclusion bodies visible on muscle biopsy, is the most common type of myopathy in patients over 50 years of age. However, it is not only under diagnosed but frequently misdiagnosed as polymyositis and hence wrongly treated with steroids. In the evaluation of progressive weakness in older Caucasian males, IBM should be an important diagnostic consideration. Treatment-resistant 'polymyositis' in patients over 50 years of age is often IBM. If there is no histological confirmation, the diagnostic criteria allow for a category of 'possible IBM'. Sometimes, the diagnosis is missed because of the slow progression of the disease and a lack of suspicion on the part of physicians. The following case report and literature review will explore many of these issues.