Disease Name
Dermatomyositis (Dermatomyositis)
Key synonyms: It is often distinguished from polymyositis (polymyositis, polymyositis), but when skin symptoms are present, the term dermatomyositis is used in particular. It is a representative disease in the myositis spectrum, and myositis-specific antibodies (e.g., anti‑Jo‑1, anti‑MDA5) may be associated.
1) Disease Description (Causes and Symptoms)
- Cause/pathophysiology: An autoimmune inflammatory disease in which immune-mediated damage to the microvasculature of the skin and skeletal muscles causes necrosis and atrophy of muscle fibers, particularly perifascicular atrophy. In some patients, viral/environmental factors or genetic susceptibility may be involved. The adult form may be associated with malignancy.
- Main symptoms:
- Gradually progressive, symmetrical proximal (shoulder and pelvic) muscle weakness (e.g., difficulty standing up, climbing stairs, combing the hair, or lifting objects)
- Skin lesions: heliotrope rash (periorbital edema and violaceous discoloration), Gottron lesions (erythema and scaling over the finger joints), and skin rashes that worsen with photosensitivity
- Systemic symptoms: fatigue, fever, myalgia, and arthralgia
- Symptoms related to complications: dysphagia (involvement of the swallowing muscles), dyspnea (respiratory muscle involvement or interstitial lung disease), and chest pain/arrhythmia (possible cardiac involvement)
- Key diagnostic findings:
- Skin lesions (in dermatomyositis) plus symmetrical proximal weakness
- Elevated serum muscle enzymes (CK, aldolase, LDH, AST/ALT)
- Abnormalities on electrophysiologic testing (EMG), evidence of inflammation on muscle MRI, and myofiber necrosis/inflammation and perifascicular atrophy on muscle biopsy
- Testing for myositis-specific/associated autoantibodies (anti‑Jo‑1, anti‑Mi‑2, anti‑MDA5, etc.) provides information on subtype and prognosis
2) Treatment Methods
- Basic principles: Control inflammation and minimize muscle damage, investigate and manage complications (ILD, dysphagia, and cancer), and restore function through rehabilitation
- Medication treatment:
- First-line: High-dose oral glucocorticoids (e.g., prednisone 0.5–1 mg/kg/day) — IV methylprednisolone pulses may be used in severe cases
- Steroid-sparing medications added early to reduce steroid side effects: methotrexate and azathioprine (azathioprine)
- Refractory/severe disease or steroid-refractory cases: IVIG (immunoglobulin), mycophenolate mofetil, cyclophosphamide, cyclosporine/tacrolimus, and biologic agents (rituximab, etc.) may be considered
- Skin symptoms: topical steroids, avoidance of photosensitivity (sun protection), and, when necessary, antimalarial agents (hydroxychloroquine), etc.
- Procedures/surgery: Although uncommon, PEG placement may be considered in cases of nutritional problems or severe dysphagia
- Rehabilitation/physical therapy: Avoid excessive muscle use during the acute phase, but after inflammation is controlled, gradual muscle strengthening and maintenance of joint range of motion are important
- Precautions during treatment:
- Increased risk of infection (when immunosuppressants are used) — check vaccination status (inactivated vaccines preferred)
- Monitor and prevent steroid side effects such as osteoporosis, hypertension, and diabetes
- Possible concurrent malignancy (particularly in adults) — cancer screening according to age and risk factors is recommended
- Lifestyle management:
- Sun protection and skin moisturization, regular nutrition and weight management, and smoking cessation
- Seek medical attention early if cold or respiratory symptoms develop (risk of ILD exacerbation)
3) Checklist Before an Outpatient Visit (Including Items to Bring and Sample Questions)
- Items/documents to bring:
- List of currently used medications (including prescription drugs, OTC drugs, herbal medicines, and supplements)
- Copies or reports of previous test results (blood tests, CK, AST/ALT, EMG/muscle MRI, muscle biopsy results, etc.)
- Timing and course of symptom onset (when they began, aggravating factors, and relieving factors)
- Records of effects and side effects after taking medications
- Notes on symptoms related to complications, such as dyspnea, dysphagia, weight changes, and fever
- Items to show the doctor during the outpatient visit:
- Recent photographs (for observing changes in the skin rash)
- Examples of functional limitations in daily life (e.g., how many stairs can be climbed, and whether daily activities can be performed independently)
- Tests/evaluations that may be needed: Blood tests (CK, infection markers, and antibodies), pulmonary function tests/chest HRCT, EMG, muscle MRI, muscle biopsy, and age-appropriate cancer screening tests
4) Examples of General Questions to Ask the Doctor
- What are the main side effects of this medication (e.g., prednisone or methotrexate), and how will they be monitored?
- What are the treatment goals and the expected recovery period (prognosis)?
- How should I manage vaccinations and infection prevention while receiving immunosuppressive treatment?
- What specifically should I be careful about regarding lifestyle habits (exercise, diet, and sun protection)?
- What tests should I undergo, and how often, because of the association with cancer (malignancy)?
5) Examples of Disease-Specific Questions
- In my case (based on my symptoms, age, and antibody results), what should cancer screening include (CT, endoscopy, tumor markers, etc.), and how often should it be performed?
- When dysphagia is severe, when should PEG (feeding tube) be considered for nutritional support or aspiration prevention?
Reference (Key points): Early diagnosis and appropriate immunosuppressive treatment and rehabilitation are important for improving the prognosis of dermatomyositis. In adult patients, the association with malignancy and lung involvement (interstitial lung disease) must be evaluated.