Makindo Medical Notes

Muscle weakness in men over 50 should raise suspicion of Inclusion Body Myositis (IBM).

About Inclusion Body Myositis

• Idiopathic inflammatory myopathy characterized by progressive muscle weakness and atrophy.
• IBM is typically less responsive to steroids and immunosuppression compared to other inflammatory myopathies.
• Most common muscle disease in individuals over 50, with a higher prevalence in men.
• Progresses slowly over many years, often leading to significant functional impairment.

Clinical Features

• Muscle Weakness: Distal and proximal muscle weakness, often asymmetrical. Affects the quadriceps, volar forearm muscles, and ankle dorsiflexors.
• Frequent Falls: Weakness in quadriceps and dorsiflexors contributes to instability and falls.
• Atrophy: Visible muscle wasting, particularly in the forearms and quadriceps.
• Swallowing Difficulties: Dysphagia is present in about 60% of cases due to pharyngeal muscle weakness.
• In some cases, associated peripheral neuropathy may be observed.

Investigations

• Creatine Kinase (CK): Usually mildly elevated compared to other inflammatory myopathies.
• Electromyography (EMG): Shows both myopathic and neurogenic changes, helping to confirm muscle involvement.
• Muscle Biopsy: Diagnostic biopsy shows characteristic findings:
  • Abnormal muscle fibers with filamentous inclusions within the nucleus and cytoplasm.
  • Vacuoles containing basophilic granules and inclusion bodies resembling Alzheimer-type filaments.
• Additional Tests: Imaging may help rule out other causes, while blood tests can exclude other inflammatory or metabolic myopathies.

Management

• Medical Management:
  • Some cases may respond to immunosuppressive therapy, though IBM generally shows limited responsiveness to steroids.
  • A specialist-led approach is necessary to tailor immunosuppressive therapy based on individual response.
• Physical Therapy:
  • Physical therapy is essential to maintain muscle strength, function, and prevent contractures.
  • Supportive devices, such as ankle-foot orthoses, may be used to assist with mobility.
• Swallowing Management:
  • Dysphagia management with dietary modifications or, if needed, enteral feeding support.
  • Speech and language therapy may aid in managing swallowing issues.
• Fall Prevention:
  • Environmental modifications, physiotherapy, and assistive devices can help reduce the risk of falls.

Outlook

• IBM is a progressive condition, but individualized management can help slow progression and enhance quality of life.
• Multidisciplinary support, including neurologists, physiotherapists, and speech therapists, is critical in managing this condition.