Dermatomyositis

Dermatomyositis is a rare autoimmune disease that causes muscle weakness and a distinctive skin rash. The body's immune system mistakenly attacks healthy muscle and skin tissue, leading to inflammation, pain, and sometimes long-term damage. It affects both adults and children and can range from mild to severe.

Muscle-related: Weakness in the upper arms, thighs, neck, or hips; Trouble climbing stairs, standing from a chair, or lifting arms; Muscle pain or tenderness; Difficulty swallowing (in some cases). Skin-related: Heliotrope rash (purplish or reddish rash around the eyes and eyelids); Gottron's papules (raised, scaly bumps over knuckles, elbows, or knees); Red or violet rashes on the face, neck, chest, back, or shoulders; Sun sensitivity. Other: Fatigue; Weight loss; Shortness of breath (if lungs are affected); Calcinosis (in children).

The exact cause is unknown but believed to be autoimmune - the immune system mistakenly attacks muscle and skin cells. Contributing factors may include genetic predisposition, viral infections, certain cancers (in adults, can be a warning sign of malignancy), or exposure to UV light.

Blood tests (look for muscle enzymes like CK and autoantibodies like anti-Mi-2 or anti-MDA5); Electromyography (EMG) to test muscle function; Muscle biopsy to look for inflammation; MRI to detect muscle inflammation; Skin biopsy if rash is present; Cancer screening may also be done in adults.

Corticosteroids (like prednisone) to reduce inflammation; Immunosuppressants (like methotrexate or azathioprine); IVIG (intravenous immunoglobulin) in severe cases; Antimalarial drugs (like hydroxychloroquine) for skin symptoms; Physical therapy to maintain strength and flexibility; Sun protection to prevent rash flare-ups.

Many people improve significantly with treatment. Some may go into remission; others have ongoing symptoms. In severe or untreated cases, complications can include permanent muscle weakness, lung disease, or difficulty swallowing. Children with juvenile dermatomyositis often respond well to treatment.

Affects approximately 1 in 100,000 people. More common in women than men. Can occur at any age - bimodal peak in children (5-15) and adults (40-60). Juvenile dermatomyositis makes up about 20% of cases.