From the Guidelines
Paraneoplastic polymyositis is a rare and severe inflammatory muscle disease associated with cancer, characterized by progressive proximal muscle weakness, elevated muscle enzymes, and characteristic inflammatory changes on muscle biopsy, requiring prompt treatment with high-dose corticosteroids and immunosuppressants to improve outcomes and quality of life 1.
Key Characteristics
- Presents with progressive, symmetric proximal muscle weakness
- Elevated muscle enzymes, particularly creatine kinase
- Characteristic inflammatory changes on muscle biopsy
- Associated with various cancers, including lung, breast, ovarian, and gastrointestinal malignancies
Management Approach
- Two-pronged approach: treating the underlying cancer and suppressing the inflammatory response
- First-line treatment: high-dose corticosteroids, such as prednisone 1 mg/kg/day, continued for 4-6 weeks before tapering based on clinical response and CK levels 1
- Steroid-resistant cases: immunosuppressants like methotrexate, azathioprine, or mycophenolate mofetil may be added
- Severe cases: intravenous immunoglobulin or rituximab may be considered for rapid improvement
Importance of Interdisciplinary Care
- Collaboration between rheumatologists and oncologists is crucial for balancing the harm and risk of oncology treatment and immunosuppressive drugs 1
- Patient-centered care: shared decision-making between patients, rheumatologists, and oncologists to discuss risks and benefits of each treatment option
Prognosis and Quality of Life
- Prognosis depends largely on successful treatment of the underlying malignancy
- Symptoms often improve when the cancer is effectively treated
- Physical therapy is essential to maintain muscle strength and prevent contractures, improving quality of life 1
From the Research
Definition and Characteristics
- Paraneoplastic polymyositis is a type of inflammatory muscle disease associated with cancer, characterized by inflammation and weakness of proximal skeletal muscles 2, 3, 4, 5, 6.
- It is a rare entity, affecting less than 1% of cancer patients, and can precede or occur simultaneously with the diagnosis or treatment of a primary tumor 4.
- The disease can manifest as a paraneoplastic syndrome, with symptoms such as progressive proximal muscle weakness, dysphagia, and dysphonia 3, 5.
Association with Cancer
- Paraneoplastic polymyositis has been associated with various types of cancer, including breast cancer 3, 4, lung cancer 5, and thyroid cancer 6.
- The underlying malignancy can determine the prognosis and life expectancy of patients with paraneoplastic polymyositis 2.
- Removal of the cancer can induce improvement of the paraneoplastic syndrome, and treatment of the underlying cancer is essential for managing the disease 3.
Diagnosis and Treatment
- Diagnosis of paraneoplastic polymyositis requires a combination of clinical features, laboratory results, and muscle biopsy 5, 6.
- Treatment often involves immunosuppressive therapy, such as corticosteroids, and may require second-line treatment with azathioprine, methotrexate, or cyclophosphicide for aggressive disease 3.
- Patient-specific examinations for detection of an underlying cancer are important in the management of patients with paraneoplastic polymyositis 2.