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  • Writer's pictureValerie Smith, APRN

Understanding Dermatomyositis and Polymyositis: Causes, Symptoms, and Management



Dermatomyositis and polymyositis are rare inflammatory muscle diseases that cause muscle weakness and can affect other parts of the body, including the skin in the case of dermatomyositis. Both conditions fall under the umbrella of idiopathic inflammatory myopathies (IIMs), characterized by chronic muscle inflammation and progressive muscle weakness. While they share similarities, each has distinct features that warrant separate consideration. 


This article explores the causes, symptoms, and management of dermatomyositis and polymyositis with sources from the National Institutes of Health. 


What are Dermatomyositis and Polymyositis?

Dermatomyositis is an inflammatory disease marked by muscle weakness and a distinctive skin rash. The condition can affect people of all ages but is more common in adults, particularly women, and children between the ages of 5 and 15.

Polymyositis involves muscle inflammation without the skin manifestations seen in dermatomyositis. It primarily affects adults, especially those in their 30s to 60s, and is more common in women.


Causes of Dermatomyositis and Polymyositis

The exact cause of both dermatomyositis and polymyositis is unknown, but they are believed to be autoimmune diseases. In autoimmune diseases, the immune system mistakenly attacks the body's own tissues. Potential contributing factors include:

  • Genetic Predisposition: Certain genetic factors may increase the risk of developing these conditions.

  • Environmental Triggers: Infections, certain medications, and other environmental factors might trigger the onset in genetically susceptible individuals.

  • Immune System Dysregulation: Abnormal immune responses play a key role in the inflammation and muscle damage seen in these conditions.


Symptoms of Dermatomyositis and Polymyositis

While both conditions share some common symptoms, each has unique clinical features:


Common Symptoms:

  • Muscle Weakness: Symmetrical weakness, typically affecting the muscles closest to the trunk, such as the thighs, hips, shoulders, upper arms, and neck.

  • Fatigue: Generalized tiredness and lack of energy.

  • Difficulty Swallowing: Dysphagia can occur due to involvement of the esophageal muscles.

  • Shortness of Breath: Muscle weakness can affect the diaphragm and other muscles involved in breathing.


Dermatomyositis-Specific Symptoms:

  • Skin Rash: A distinctive rash often appears on the face, eyelids, knuckles, elbows, knees, chest, and back. The rash can be violet or dusky red and may be itchy or painful.

  • Gottron's Papules: Raised, scaly bumps over the knuckles, elbows, and knees.

  • Heliotrope Rash: A violet or dusky discoloration of the eyelids, often accompanied by swelling.

  • Calcinosis: Calcium deposits under the skin, more common in children with dermatomyositis.


Diagnosis of Dermatomyositis and Polymyositis

Diagnosing these conditions involves a combination of clinical evaluation, laboratory tests, and imaging studies:

  • Medical History and Physical Examination: A detailed history and examination of muscle strength and skin changes.

  • Blood Tests: Elevated levels of muscle enzymes (e.g., creatine kinase) indicate muscle damage. Autoantibodies specific to inflammatory myopathies may also be present.

  • Electromyography (EMG): Assesses electrical activity in muscles and can reveal patterns consistent with myopathy.

  • Muscle Biopsy: A small sample of muscle tissue is examined under a microscope to identify inflammation and other characteristic changes.

  • Magnetic Resonance Imaging (MRI): Detects inflammation in muscles and helps guide biopsy sites.


Management and Treatment

While there is no cure for dermatomyositis or polymyositis, treatments aim to reduce inflammation, improve muscle strength, and manage symptoms. Treatment plans are often individualized and may include:

  1. Medications:

  • Corticosteroids: Prednisone is commonly used to reduce inflammation. Long-term use requires careful monitoring for side effects.

  • Immunosuppressive Drugs: Medications such as methotrexate, azathioprine, and mycophenolate mofetil help control the immune system and reduce inflammation.

  • Biologic Agents: Rituximab and other biologics are used in cases resistant to standard treatments.

  • Intravenous Immunoglobulin (IVIG): Used for severe or refractory cases.

  1. Physical Therapy: A tailored exercise program helps maintain and improve muscle strength, flexibility, and function. Physical therapists can design specific routines to avoid muscle overuse and injury.

  2. Occupational Therapy: Assists patients in adapting to daily activities and improving their quality of life. This may include using assistive devices and modifying tasks to reduce strain on muscles.

  3. Speech Therapy: For those with swallowing difficulties, speech therapists provide techniques and exercises to improve swallowing function.

  4. Sun Protection: For dermatomyositis patients, protecting the skin from UV exposure is crucial. Sunscreen, protective clothing, and avoiding peak sun hours help prevent rash exacerbation.

  5. Regular Monitoring: Ongoing assessment by healthcare providers to monitor disease progression, medication side effects, and adjust treatment plans as necessary.


Prognosis

The prognosis for dermatomyositis and polymyositis varies. With early diagnosis and appropriate treatment, many patients experience significant improvement in symptoms and quality of life. However, some may have persistent muscle weakness or complications related to the disease or its treatment. In severe cases, involvement of the lungs, heart, or other organs can lead to more serious outcomes. Regular follow-up and comprehensive care are essential for managing these conditions effectively.


Dermatomyositis and polymyositis are complex inflammatory muscle diseases that require a multidisciplinary approach for effective management. Understanding the causes, recognizing the symptoms, and implementing appropriate treatment strategies can significantly improve the lives of those affected. 


If you experience unexplained muscle weakness or skin changes, seeking medical advice promptly can lead to early diagnosis and better outcomes. Paducah Rheumatology is accepting new patients with a required physician's referral. Call 270-408-6100 to schedule an appointment with our healthcare team. 


Through a combination of medications, therapies, and lifestyle adjustments, individuals with these conditions can manage their symptoms and maintain a good quality of life.

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