Inclusion Body Myositis

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💪 In men over 50, progressive muscle weakness should raise suspicion of Inclusion Body Myositis (IBM).

About Inclusion Body Myositis

• 🧩 Idiopathic inflammatory myopathy with slow progression.
• 💊 Unlike polymyositis/dermatomyositis, IBM is poorly responsive to steroids and immunosuppressants.
• 👴 Most common acquired muscle disease in people >50 years, especially men.
• 🐢 Progresses slowly over years, leading to falls, disability, and swallowing problems.

🩺 Clinical Features

• ⚡ Muscle Weakness: Asymmetrical; distal + proximal involvement (quadriceps, finger flexors, ankle dorsiflexors).
• 🤕 Frequent Falls: Quadriceps and foot dorsiflexor weakness → instability.
• 📉 Atrophy: Wasting in forearms and quadriceps.
• 🥤 Dysphagia: Affects ~60% of patients due to pharyngeal muscle weakness.
• 🔌 May have associated peripheral neuropathy in some cases.

🔎 Investigations

• 🧪 CK (Creatine Kinase): Mildly raised (unlike polymyositis).
• ⚡ EMG: Mixed myopathic + neurogenic changes.
• 🔬 Muscle Biopsy: Pathognomonic findings:
  • Intranuclear + cytoplasmic inclusions with filamentous material.
  • “Rimmed vacuoles” containing basophilic granules.
  • Inclusion bodies resembling Alzheimer-type filaments.
• 🖼️ Imaging/blood tests: Exclude metabolic or autoimmune myopathies.

💊 Management

• 💊 Medical: Limited response to steroids; some cases trial immunosuppressants. Specialist-led care needed.
• 🏃 Physiotherapy: To preserve strength, prevent contractures; ankle-foot orthoses may aid walking.
• 🥄 Swallowing support: Diet modifications, SLT input, enteral feeding if severe.
• 🛡️ Fall prevention: Home adaptations, physiotherapy, walking aids.

Outlook

• 📉 Progressive, but individualized therapy slows decline.
• 🤝 Multidisciplinary care (neurology, physio, SLT, OT) essential for best quality of life.

Cases - Inclusion Body Myositis (IBM)

• Case 1 - Finger Flexor Weakness ✊: A 68-year-old man presents with difficulty gripping objects and frequent dropping of tools. Exam: weakness of finger flexors and quadriceps, asymmetric. Reflexes preserved, no sensory loss. CK mildly elevated. Diagnosis: Inclusion body myositis. Management: Supportive - physiotherapy, occupational therapy, falls prevention, mobility aids. Poor response to steroids.
• Case 2 - Falls from Quadriceps Weakness 🚶: A 72-year-old woman reports recurrent falls and trouble rising from a chair. Exam: marked quadriceps wasting and weakness, with sparing of hip adductors. Finger flexor weakness also present. Diagnosis: IBM with classic quadriceps involvement. Management: Supportive rehabilitation, walking aids, home adaptations; palliative MDT input in advanced disease.
• Case 3 - Dysphagia as a Complication 🍽️: A 70-year-old man with known IBM develops progressive difficulty swallowing solids, coughing when eating, and recurrent chest infections. Diagnosis: IBM with oropharyngeal dysphagia. Management: Speech and language therapy; modified diet; gastrostomy if severe; supportive care.

Teaching Commentary 🧠

Inclusion body myositis is the most common acquired myopathy in adults >50. It presents with insidious, asymmetric weakness - especially of quadriceps and finger flexors (unlike polymyositis/dermatomyositis). CK is mildly elevated, EMG shows myopathic changes, and muscle biopsy confirms rimmed vacuoles with protein inclusions. Key features: - Slowly progressive, resistant to steroids (helps distinguish from polymyositis). - Falls and hand weakness are early clues. - Dysphagia occurs in ~50% and is a major morbidity cause. Management is supportive and rehabilitative, as there is no proven disease-modifying therapy. Prognosis: gradual decline in mobility and independence.