Dermatomyositis

Dermatomyositis is a rare autoimmune inflammatory disease affecting the skin and skeletal muscles. It is characterized by distinctive skin rashes together with progressive symmetrical proximal muscle weakness. The disease may also involve the lungs, heart, and gastrointestinal tract and is associated with an increased risk of malignancy in adults.

Pathophysiology (Brief)

The disease is caused by autoimmune-mediated inflammation affecting:

• Skeletal muscles

• Small blood vessels

• Skin

This leads to muscle fiber damage and characteristic skin manifestations.

Signs & Symptoms

Skin manifestations

• Gottron papules

• Heliotrope rash

• Photosensitive rash

Muscle manifestations

• Progressive proximal muscle weakness

• Difficulty combing hair

• Difficulty climbing stairs

• Difficulty rising from a squatting position

• Difficulty lifting objects

Other features

• Fatigue

• Muscle tenderness

• Difficulty swallowing in severe disease

Diagnostic Criteria

Diagnosis is based on:

• Typical skin lesions

• Symmetrical proximal muscle weakness

• Elevated muscle enzymes

• Supportive laboratory and biopsy findings

Investigations

• Full blood picture

• ESR

• Liver function tests

• Renal function tests

• Creatine kinase (CK)

• ANA

• Muscle or skin biopsy when indicated

Monitoring

• Blood count, liver function, and renal function every 3 months

• Random blood glucose every 3 months during prolonged corticosteroid therapy

Treatment

Non-pharmacological treatment

• Use sunscreen and protective clothing

• Physiotherapy

• Monitor blood pressure

• Involve a physician

• Ophthalmology review when hydroxychloroquine is prescribed

• Deworm with Albendazole 400 mg stat before prolonged immunosuppressive therapy where appropriate

Pharmacological treatment

• Prednisolone (PO) 1 mg/kg once daily for 12 weeks until improvement, then gradually taper to the lowest effective dose

AND

• Methotrexate (PO) 7.5–20 mg once weekly for at least 6 months

Complications

• Progressive muscle weakness

• Dysphagia

• Interstitial lung disease

• Cardiac involvement

• Malignancy

• Permanent disability

Patient counselling

• Dermatomyositis is a chronic autoimmune disease requiring long-term follow-up.

• Continue physiotherapy to maintain muscle strength.

• Protect the skin from sunlight.

• Report worsening muscle weakness, swallowing difficulty, or breathing problems immediately.

• Regular monitoring is essential while receiving immunosuppressive therapy.