Polymyositis (PM) and Dermatomyositis (DM)

Polymyositis (PM) and Dermatomyositis (DM) are rare inflammatory myopathies, a group of disorders characterized by muscle weakness and inflammation.

While they share many similarities, Dermatomyositis is distinguished by skin manifestations in addition to the muscle symptoms seen in Polymyositis. Both conditions are believed to have an autoimmune origin, where the immune system mistakenly attacks the body's tissues, but they may also involve environmental and genetic factors.

What Are the Signs/Symptoms?

• Polymyositis:

  • Progressive, symmetric muscle weakness, typically affecting proximal muscles (shoulders, hips, neck).
  • Difficulty with activities requiring muscle strength, such as climbing stairs or lifting objects.
  • Muscle tenderness or discomfort.
  • In severe cases, complications like difficulty swallowing (dysphagia) or breathing issues can arise.

• Dermatomyositis:

  • All symptoms of Polymyositis.
  • Skin changes, such as a heliotrope rash (purplish discoloration around the eyes), Gottron’s papules (raised, scaly bumps over knuckles and joints), and photosensitivity.
  • Red or purple rash on the chest, back, or other exposed areas.
  • Calcinosis, a condition where calcium deposits form under the skin, may occur in chronic cases, particularly in children.

What Are Common Treatments?

Treatment is aimed at reducing inflammation, improving muscle strength, and managing symptoms:

• Corticosteroids: Prednisone is often the first-line treatment to control inflammation.
• Immunosuppressive Drugs: Methotrexate, azathioprine, or mycophenolate mofetil may be used for patients who do not respond to corticosteroids or to minimize steroid side effects.
• Physical Therapy: Helps maintain mobility and muscle strength.
• Skin Protection: For Dermatomyositis, sunscreen and protective clothing are essential to manage photosensitivity.
• Intravenous Immunoglobulin (IVIG): Used in severe or refractory cases.
• Cancer Screening: Recommended for patients with Dermatomyositis due to the increased cancer risk.