Dermatomyositis

Question 1

Definition & pathogenesis

Answer 1

Autoimmune Inflammatory disorder involving the skin and the muscles
Molecular mimicry: host protein mimiking tumor or foreign protein –> activating complement
Polumyositis has no skin involvement
The complement activation damages the blood vessles leading to skin and muscle ischemia

Question 2

Age & groups affected

Answer 2

children or adults >50

Associated with cancer, paraneoplastic disease

Question 3

Symptoms in muscles

Answer 3

Bilateral weakness, muscle atrophy muscle pain and tenderness mostly in proximal, big muscle groups, like the shoulder or hip
In severe cases, the muscles of the pharynx or esophagus can be affected causing dysphagia, or difficulty in swallowing.
Weight loss

Question 4

Symptoms in skin

Answer 4

purplish rash on the upper eyelids, called a “heliotrope rash”: purple periorbital erythema and edema
purple papules and plaques, telangiectasis on the dorsal surface of fingers, around nail folds
“shawl” rash involving the shoulders, upper chest, and back
Malar rash
Gottron’s sign: flat, red, scaly papules over the back of the fingers, elbows, or knees. photosensitive, itchy, painful, and can bleed

Question 5

Diagnosis

Answer 5

Symptoms/signs
Autoantiboides: anti-Mi2, anti Jo1, ANA
Muscle enzymes: CK
Muscle biopsy:  Perimysium inflammation
Abnormal EMG
AST
LDH
MRI
Exclude cancer

Question 6

Treatment

Answer 6

Sun protection
Systemic Corticosteroids
Immunosupression: methotrexate, azathioprine, ciclosporin, mycophenolate, cyclophosphamide and high-dose intravenous immunoglobulin
Antimalarial medications for the rash
Physiotherapy

Question 7

Malignancies associated with dermatomyositis

Answer 7

Involve the ovary, breast, lung and gastrointestinal tract.