Clinical features of inclusion body myositis (IBM)

Ashton, 2021Needham, 2016Schmidt, 2018

Note: Inclusion body myositis is the most common acquired muscle disease in adults older than 50 years and is resistant to pharmacological treatment.

Although rare, inclusion body myositis (IBM) is the most common acquired muscle disease in adults older than 50 years and is 2 to 3 times more common in malesSchmidt, 2018. Consider IBM when an older male presents with new muscle weakness that also involves more distal muscles (compared with the other inflammatory myopathies).

IBM is distinct in clinical presentation and pathology from the other idiopathic inflammatory myopathies. It has a specific pattern of wasting and weakness, affecting the long flexor muscles of the fingers and knee extensor (quadriceps) muscles. People often present with falls, difficulty going up or down stairs or rising from low chairs.

IBM has a progressive course and is not very responsive to pharmacological treatments. For example, dysphagia is a prominent symptom in IBM that does not improve with standard immunomodulatory treatment. Patients may need enteral nutrition support. Management for IBM is outlined in Specific management for inclusion body myositis.