inclusion body myositis (IBM)

see also:

• polymyositis (PM)
• dermatomyositis

• rare but increasingly prevalent (with the aging population) chronic inflammatory myopathy
• slowly progressive weakness and wasting of both distal and proximal muscles, of both arms and legs, and unlike polymyositis (PM) and dermatomyositis, responds poorly to corticosteroids and other immunosuppressants

• mixed autoimmune and degenerative processes
• incidence increases with age and symptoms usually begin after 50 years of age
• 50 cases per million in those aged over 50 years (compared with 15 cases per million in all ages)
• the most common acquired muscle disorder seen in people over 50
• 20% have onset before age 50yrs
• weakness comes on slowly (over months or years)
• slightly more common in men than women
• may become unable to perform daily living activities and most require assistive devices within 5 to 10 years of symptom onset
• may cause potentially fatal dysphagia
• no effective treatment exists

• occurs in siblings but not passed to children

• heterogeneous group of very rare hereditary conditions
• IBM2:
  • mainly Iranian Jew ethnicity
  • if the quadriceps are spared but the hamstrings and iliopsoas are severely affected in a person between ages of 20-40, it is very likely IBM2 will be at the top of the differential diagnosis.
• see wikipedia

• raised creatinine kinase (CK)
• muscle biopsy:
  • inclusion bodies, rimmed vacuoles and accumulation of aberrant proteins similar to those found in senile plaques of Alzheimer's disease