Dermatomyositis and Polymyositis

Introduction

Dermatomyositis and polymyositis are rare autoimmune disorders that affect the muscles and skin. These conditions can cause muscle weakness, skin rashes, and other symptoms. This guide aims to provide an overview of dermatomyositis and polymyositis, including their clinical features, diagnostic criteria, and treatment options.

Clinical Features

Dermatomyositis

• Muscle weakness: Proximal muscles, such as those in the hips, thighs, shoulders, and upper arms, are primarily affected. This weakness can lead to difficulty climbing stairs, rising from a seated position, or lifting objects.
• Skin manifestations: Patients may develop a distinctive rash on the upper eyelids and cheeks, known as the "heliotrope rash." Other skin abnormalities include a reddish or bluish-purple rash on the knuckles or elbows (Gottron's papules), a scaly rash on the scalp (scalp involvement), and a rash on the chest or back (V-sign and shawl sign).
• Systemic symptoms: Some individuals may experience fatigue, fever, weight loss, and sensitivity to light (photosensitivity).

Polymyositis

• Muscle weakness: Similar to dermatomyositis, polymyositis primarily affects the proximal muscles, resulting in difficulties with climbing stairs, lifting objects, and other activities.
• Absence of skin manifestations: Unlike dermatomyositis, polymyositis does not present with characteristic skin rashes.

Diagnostic Criteria

The diagnosis of dermatomyositis and polymyositis is based on a combination of clinical features, laboratory tests, and muscle biopsies. The following criteria are commonly used:

1. Symptom duration: Symptoms should persist for at least 3-4 months.
2. Clinical features: The presence of characteristic muscle weakness and skin manifestations (in dermatomyositis).
3. Laboratory tests:
   • Elevated muscle enzymes: Creatine kinase (CK) and aldolase levels are often increased.
   • Autoantibodies: Around 60-80% of dermatomyositis cases are positive for anti-nuclear antibodies (ANA), anti-Mi-2, or anti-Jo-1 antibodies.
4. Muscle biopsy: This is an essential step to confirm the diagnosis. Findings may include muscle fiber inflammation, necrosis, or atrophy.

Treatment Options

The management of dermatomyositis and polymyositis involves a multidisciplinary approach, including rheumatologists, dermatologists, and physiotherapists. The treatment aims to control inflammation, improve muscle strength, and manage skin manifestations. The following interventions are commonly employed:

1. Medications:
   • Corticosteroids: High-dose oral or intravenous steroids (e.g., prednisone) are typically the first-line treatment.
   • Immunosuppressants: Additional drugs, such as methotrexate, azathioprine, or mycophenolate mofetil, may be used to reduce the need for long-term steroid use.
   • Biologics: In refractory cases, biologic agents like rituximab or intravenous immunoglobulin (IVIG) may be considered.
2. Physical therapy: Regular exercise and physical therapy help maintain muscle strength, improve mobility, and prevent complications like contractures.
3. Sun protection: Due to photosensitivity, patients should use sunscreens, wear protective clothing, and limit sun exposure.
4. Regular monitoring: Routine follow-up visits are essential to assess treatment response, manage potential side effects, and address disease complications.

Conclusion

Dermatomyositis and polymyositis are autoimmune disorders characterized by muscle weakness and, in the case of dermatomyositis, skin rashes. Diagnosing these conditions often involves a combination of clinical features, laboratory tests, and muscle biopsies. Treatment mainly focuses on reducing inflammation, improving muscle strength, and managing skin manifestations. A comprehensive approach involving various healthcare professionals helps optimize patient outcomes.