Inclusion body myositis

A progressive muscle disorder

Inclusion body myositis
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Synonyms	sIBM
Pronounce
Field	Rheumatology, Neurology, Neuromuscular medicine
Symptoms	Progressive muscle weakness, muscle wasting
Complications	Mobility issues, difficulty swallowing (dysphagia)
Onset	Typically after age 45
Duration	Chronic, lifelong
Types	Sporadic inclusion body myositis (sIBM), Hereditary IBM
Causes	Unknown, possibly autoimmune and degenerative
Risks	Advanced age, genetic predisposition
Diagnosis	Muscle biopsy, clinical assessment, electromyography (EMG)
Differential diagnosis	Deconditioning, hereditary muscle diseases, polymyositis, dermatomyositis
Prevention	None known
Treatment	Supportive therapies (physical therapy, occupational therapy), symptomatic management
Medication	Immunotherapy generally ineffective; symptomatic medications as needed
Prognosis	Slowly progressive disability, typically non-fatal
Frequency	5-71 per 1,000,000
Deaths	Rarely directly fatal; associated complications can increase risk

Inclusion body myositis (IBM), specifically sporadic inclusion body myositis (sIBM), is a chronic, slowly progressive inflammatory muscle disease characterized primarily by progressive muscle weakness and wasting. It predominantly affects older adults, typically beginning after the age of 45.

Signs and Symptoms

Symptoms generally develop slowly and include:

• Progressive weakness in the forearms, wrists, thighs, and muscles controlling finger flexion
• Difficulty swallowing (dysphagia)
• Gradual muscle atrophy, especially in the quadriceps and forearm muscles

Causes

The exact cause of IBM remains unknown. The condition is thought to involve both autoimmune and degenerative processes, possibly influenced by genetic factors.

Risk Factors

Factors increasing the likelihood of developing IBM include:

• Advanced age, typically over 45
• Genetic susceptibility

Diagnosis

Diagnosis typically involves:

• Clinical evaluation and detailed patient history
• Electromyography (EMG) to assess muscle activity
• Muscle biopsy revealing characteristic inclusions and inflammation

Differential diagnosis should consider:

• Deconditioning
• Hereditary muscle diseases
• Polymyositis
• Dermatomyositis

Treatment

There is currently no curative treatment for IBM. Management primarily includes:

• Physical therapy and occupational therapy to maintain mobility and functionality
• Supportive interventions such as speech therapy for dysphagia

Immunotherapy typically has limited or no benefit in IBM patients.

Prognosis

IBM progresses slowly, causing increasing disability but rarely affecting life expectancy directly. However, complications such as severe swallowing difficulties can contribute to health risks.

Epidemiology

IBM is a relatively rare condition, with prevalence estimates ranging from 5 to 71 cases per million people worldwide, making it one of the most common inflammatory muscle diseases in adults over 50.

Prevention

No known preventive measures exist for inclusion body myositis.

Related pages

• Inflammatory myopathy
• Autoimmune disease
• Muscle biopsy
• Neurodegenerative disease