IBM

Inclusion body myositis (IBM)

Name: ___________________________________________________________

Date of birth: ______________________________________________________

Emergency contact: ________________________________________________

GP name: ________________________________________________________

GP contact: ______________________________________________________

If presenting at an emergency department, contact the neurology/neuromuscular team and respiratory team at: _________________________________________

as soon as possible on: _____________________________________________

IBM is a late onset, slowly progressive muscle-wasting condition. It is associated with falls, dysphagia and varying degrees of respiratory involvement but not cardiac or central nervous system impairment. The condition does not restrict lifespan.

IBM is the most common cause of a late onset myopathy in people over the age of 50, affecting around 1 in 100,000 people in the UK. The mean age of onset is 62 years and it rarely occurs in people under the age of 40.

A characteristic pattern of very slowly progressive weakness of grip strength and proximal weakness in the legs occurs in most. Less frequent initial symptoms include swallowing difficulties or foot-drop. Right-handed people usually experience a greater degree of weakness on their left side, and vice versa.

The cause of IBM is poorly understood but the muscle biopsy shows features of inflammation, mitochondrial abnormality and abnormal deposit of various proteins. Creatine kinase (CK) is moderately elevated or normal. It is not considered a primarily genetic condition.

Falls and mobility

The most frequently affected muscles are the quadriceps and forearm muscles. Falls are therefore common particularly on rough ground or on stairs. It is often impossible to stand up after a fall without assistance. Walking frames or rollators are usually more helpful for reducing falls than walking sticks. While regular exercise is encouraged, targeted strength training exercises for quadriceps should be avoided.

Stairs or steps are particularly difficult and it may be necessary to use a chairlift. Chair leg raisers, cushions or rise-recliner chairs should be used to assist with standing from low seating. Grip weakness affects writing, dexterity and using cutlery.

Respiratory impairment

Some impairment of respiratory muscle strength is common but this rarely requires intervention.

Swallowing difficulties

  • About 50 percent of patients experience swallowing difficulties because of pharyngeal muscle weakness. As a result of swallowing difficulties, and to avoid choking, patients may need to modify their diet and to eat slowly. This is particularly true of solid dry food.
  • Dietary supplements or a gastrostomy feeding tube may be necessary.
  • In combination with respiratory weakness, there is an increased risk of aspiration pneumonia.
  • Swallowing difficulties may be temporarily worsened by intercurrent or systemic illness.

Medication and anaesthetic precautions

  • It is essential that the anaesthetist is aware of the diagnosis of IBM to allow appropriate pre-operative assessment and post-operative monitoring.
  • Local anaesthetics and nitrous oxide are safe (for example, for minor dental procedures).
  • Statins are usually well tolerated but caution should be exercised at high doses. There is a risk of side-effects in the muscles, which will exacerbate existing muscle weakness.
  • Immunisations should be kept up-to-date, including flu vaccine.
  • Immunosuppression does not help the majority of patients with IBM and should only be given under expert neuromuscular care.