Polymyositis and Dermatomyositis (3)

Question 1

What is Polymyositis?

What is Dermatomyositis?

Answer 1

➊ Chronic inflammation of muscles

➋ Chronic inflammation of skin and muscles

Question 2

What is the main presenting feature of Polymyositis?
→ What may occur as the disease progresses?

What is another feature of Polymyositis?

What are the features of Dermatomyositis?

Answer 2

➊ Typically bilateral, proximal (shoulders and pelvic girdle) muscle weakness, developing over wks-months
→ There may be pharyngeal, oesophageal and respiratory muscle involvement, leading to dysphonia, dysphagia, and T2 resp failure, respectively

➋ Muscle pain, fatigue, and weakness

➌ Presents with the features of Polymyositis + Skin features:
• Heliotrope rash (lilac discolouration of eyelid with periorbital oedema)
• Gottron lesions (scaly erythematous patches) on joints
• Macular erythematous rash

Question 3

Investigations:
What is the key investigation finding here?
→ What are other causes of this being raised?

What other investigations may be done?

What is done for a definitive diagnosis?
→ What will this show?

Answer 3

➊ Raised CK
→ Rhabdomyolysis, AKI, MI, Statins, Strenuous exercise

➋ • EMG – Confirms myopathic cause, and excludes a neuropathic cause
• Anti-Jo-1, Anti-Mi-2

➌ Muscle biopsy
→ Inflammatory infiltrates

Question 4

What is used to manage it?
→ What may be added alongside this? How does this help?

Answer 4

Corticosteroids
→ Immunosuppressants/DMARDs e.g. methotrexate – This makes it easier for the steroids to work, therefore not needing as high a dose