What is the diagnosis and treatment for muscular necrosis (myopathy)?

From the Guidelines

Myopathy necrosis, also known as muscular necrosis, is a serious condition that requires immediate medical attention, and the cornerstone of initial treatment is high-dose corticosteroids, which should be administered as a bolus in severe cases, as recommended by the American Society of Clinical Oncology clinical practice guideline 1. The diagnosis of myopathy necrosis involves a combination of clinical evaluation, laboratory tests, and imaging studies. Common symptoms include muscle weakness, pain, swelling, and elevated creatine kinase levels in the blood. The condition can be caused by multiple factors, including autoimmune conditions, toxins, medications, infections, or genetic disorders. Some key points to consider in the diagnosis and treatment of myopathy necrosis include:

• The clinical presentation of patients with immune-related myositis can vary and affect large and/or small joints, with symptoms such as arthralgia, myalgia, and weakness 1.
• Laboratory tests, such as serum inflammatory markers and autoantibody panels, can help diagnose and differentiate myopathy necrosis from other conditions 1.
• Imaging studies, such as MRI and EMG, can provide useful information to identify a muscle site for biopsy, diagnose myositis, and monitor treatment response 1.
• Treatment depends on the underlying cause, but often includes stopping any offending medications, providing supportive care, and addressing the specific etiology, with corticosteroids being a common treatment option for inflammatory myopathies 1.
• Physical therapy is often beneficial to maintain muscle function and prevent contractures, and early diagnosis and intervention are crucial to prevent extensive muscle destruction and improve outcomes 1. It is essential to note that the prognosis varies widely depending on the cause, with some cases resolving completely with appropriate treatment while others may lead to permanent muscle damage. Therefore, a comprehensive and multidisciplinary approach to diagnosis and treatment is necessary to optimize outcomes for patients with myopathy necrosis.

From the FDA Drug Label

An acute myopathy has been observed with the use of high doses of corticosteroids, most often occurring in patients with disorders of neuromuscular transmission (e.g., myasthenia gravis), or in patients receiving concomitant therapy with neuromuscular blocking drugs (e.g., pancuronium). This acute myopathy is generalized, may involve ocular and respiratory muscles, and may result in quadriparesis. Elevation of creatinine kinase may occur. Clinical improvement or recovery after stopping corticosteroids may require weeks to years

• Diagnosis of muscular necrosis (myopathy) may involve elevated creatinine kinase levels and clinical presentation of muscle weakness.
• Treatment for muscular necrosis (myopathy) caused by corticosteroids may involve stopping or reducing the corticosteroid dosage, as clinical improvement or recovery may require weeks to years 2.

From the Research

Diagnosis of Muscular Necrosis (Myopathy)

• The diagnosis of immune-mediated necrotizing myopathy (IMNM) is based on clinical findings, such as progressive proximal muscle weakness, elevated serum creatine kinase (CK) levels, and necrotic muscle fibers with minimal inflammation on muscle biopsy 3, 4, 5.
• Electromyography may show a myopathic pattern, and muscle biopsy can confirm the presence of necrosis and regeneration fibers 4.
• The presence of specific autoantibodies, such as anti-signal recognition particle (SRP) or anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibodies, can also support the diagnosis of IMNM 4, 5.

Treatment of Muscular Necrosis (Myopathy)

• There is no standard treatment strategy for IMNM, but various immunotherapies have been used to treat the condition, including high-dose glucocorticoids, tacrolimus, intravenous immunoglobulins, and rituximab 3, 4, 6, 5.
• Early initiation of intensive combined therapy, including intravenous immunoglobulins and tacrolimus, may be effective in preventing irreversible muscle damage and improving clinical outcomes in patients with IMNM 3.
• Corticosteroids, such as prednisone, may also be effective in treating IMNM, particularly in patients with anti-SRP antibody-positive subsets 4, 6.
• Rituximab may be considered as a treatment option for patients with IMNM who are refractory to steroids and multiple immunotherapies, particularly in African Americans with anti-SRP antibody-positive subsets 5.
• Other immunosuppressive drugs, such as azathioprine, cyclosporine, mycophenolate, or methotrexate, may offer some benefit as steroid-sparing agents, but their effectiveness is limited 6.