Can inflammatory myositis relapse?

Inflammatory Myositis Can Relapse

Yes, inflammatory myositis can relapse in approximately two-thirds of patients, with recurrence of muscle or cutaneous manifestations requiring increased glucocorticoid dosage after initial improvement. 1

Relapse Patterns and Risk Factors

• Inflammatory myopathies, including dermatomyositis (DM), polymyositis (PM), and immune-mediated necrotizing myopathy (IMNM), commonly follow a relapsing course despite initial treatment success 2, 1
• In a study of 105 patients with idiopathic inflammatory myopathies (IIMs), 65 patients (62%) experienced relapse during follow-up 1
• Relapse is characterized by recurrence of muscle weakness, elevated muscle enzymes, or characteristic skin manifestations after initial improvement 2, 1
• Higher antinuclear antibody (ANA) titers are associated with increased relapse risk 1
• Histopathologic features consistent with IIMs are significantly associated with higher relapse rates (HR 1.69) 1

Protective Factors Against Relapse

• The use of immunosuppressants during the initial glucocorticoid tapering phase significantly reduces relapse risk (HR 0.50) 1
• Early initiation of steroid-sparing agents concurrent with corticosteroids, as recommended by the Mayo Clinic, helps prevent relapses 3
• Combination therapy with high-dose corticosteroids and steroid-sparing agents such as methotrexate, azathioprine, or mycophenolate mofetil improves long-term outcomes 3, 4

Clinical Course and Monitoring

• Relapses typically occur during steroid tapering or after reaching low-dose maintenance therapy 2, 1
• Disease course can be non-relapsing in approximately 73% of patients with proper management 5
• Regular monitoring of muscle enzymes (especially creatine kinase) and inflammatory markers is essential to detect early signs of relapse 4
• Serial assessment of muscle strength and function helps identify clinical relapses before significant weakness develops 4
• MRI can be useful for monitoring treatment response and detecting subclinical disease activity 3, 4

Treatment of Relapses

• For mild-moderate relapses, increasing corticosteroid dose is the initial approach, typically to 1 mg/kg/day of prednisone or equivalent 4
• For severe relapses with significant muscle weakness or extramuscular involvement, high-dose methylprednisolone may be required 3
• Addition or change of steroid-sparing agents should be considered with each relapse 4
• For refractory disease with multiple relapses, more aggressive therapy may be needed, including:
  • Intravenous immunoglobulin (IVIG) at 2 g/kg divided over 2-5 days 4
  • Rituximab, especially for antibody-positive disease 3
  • Cyclophosphamide for severe or life-threatening disease 3, 4

Special Considerations

• Patients with dermatomyositis may initially present with only muscle symptoms and develop characteristic skin manifestations later in the disease course 6
• Immune checkpoint inhibitor-induced myositis can have a fulminant course with high mortality, especially when myocarditis or myasthenia gravis coexist 3, 4
• Medication-induced myositis (e.g., from statins) typically improves when the offending agent is discontinued, but may occasionally follow a chronic course 3, 7

Prognosis

• With appropriate treatment, approximately 80% of patients can achieve remission 5
• About 20% of patients may achieve complete remission off all medications 5
• Damage accumulation occurs in approximately 37% of patients despite treatment 5
• Delayed diagnosis (>1 year of symptoms) is associated with chronic-continuous disease course, greater damage, and need for more aggressive immunosuppression 5

Understanding the relapsing nature of inflammatory myopathies is crucial for developing appropriate long-term management strategies and setting realistic expectations for patients.