How is steroid-induced myopathy managed?

Management of Steroid-Induced Myopathy

The primary management of steroid-induced myopathy involves dose reduction or discontinuation of the corticosteroid medication, along with implementation of a steroid-sparing agent to maintain treatment of the underlying condition. 1, 2

Clinical Presentation and Diagnosis

• Steroid-induced myopathy typically presents as proximal muscle weakness that can interfere with activities of daily living, often painless and developing insidiously 2
• Acute myopathy can develop rapidly (within 1-3 days) after steroid initiation, even with a single dose, while chronic myopathy develops after prolonged treatment 3
• Muscle enzymes including CK, LDH, and aldolase typically show minimal elevation, making laboratory diagnosis challenging 1
• Respiratory muscles may be affected even when proximal limb muscles remain relatively strong, potentially leading to symptomatic dyspnea 4, 5

Management Algorithm

Step 1: Recognition and Assessment

• Maintain high index of suspicion for steroid myopathy in any patient on corticosteroid therapy presenting with muscle weakness 3
• Evaluate for proximal muscle weakness affecting hip flexion, shoulder abduction, and activities like rising from a seated position 2
• Assess respiratory function, as respiratory muscle involvement may occur independently of limb weakness 4, 5

Step 2: Corticosteroid Modification

• Reduce corticosteroid dose when possible, as weakness is significantly related to cumulative steroid dose 4
• Consider switching from fluorinated steroids (like dexamethasone) to non-fluorinated steroids (like prednisone) as side effects occur more frequently with fluorinated steroids 5
• Implement a steroid-sparing agent concurrently with dose reduction to maintain treatment of the underlying condition 6, 7

Step 3: Steroid-Sparing Agents

• Initiate one of the following steroid-sparing agents based on the underlying condition:
  • Methotrexate: Start at 15 mg weekly with 1 mg/day folic acid supplementation, targeting 25 mg weekly within 3-6 months 6
  • Azathioprine: Target dose of 2 mg/kg of ideal body weight in divided doses, starting at 25-50 mg/week with increments of 25-50 mg/week 6
  • Mycophenolate mofetil: Start at 500 mg twice daily, increasing by 500 mg weekly until reaching 1000 mg twice daily 6

Step 4: For Severe or Refractory Cases

• Consider IVIG therapy (1-2 g/kg) for patients with severe weakness (Grade 3-4) who have inadequate response to corticosteroids 8
• For inflammatory myopathies with severe manifestations, consider pulse methylprednisolone (10-20 mg/kg or 250-1000 mg for 1-5 consecutive days) before transitioning to oral steroids 7

Supportive Measures

• Implement a structured exercise program focusing on resistance training to counteract muscle atrophy 1
• Consider nutritional support with branched-chain amino acids, which may help address the imbalance between anabolism and catabolism of muscle proteins 1
• Monitor respiratory function regularly, especially in patients with underlying pulmonary conditions like COPD 5

Prognosis

• Improvement or resolution of weakness can be expected in most patients following steroid reduction or discontinuation 4
• Recovery time varies, with some patients showing improvement within weeks while others may require several months 2, 4
• In cases of acute steroid myopathy, irreversible damage may occasionally occur, emphasizing the importance of early recognition 3

Common Pitfalls to Avoid

• Failing to recognize steroid myopathy and erroneously attributing weakness to the underlying disease process 3
• Overlooking respiratory muscle involvement, which can occur independently of limb muscle weakness 4, 5
• Delaying initiation of steroid-sparing agents, which should be started concurrently with corticosteroids in many conditions 6, 7
• Neglecting to check IgA levels before administering IVIG in severe cases requiring this therapy 8