Dermatomyositis

Question 1

What is dermatomyositis?

Answer 1

Myositis = inflammation of striated muscle causing proximal muscle weakness

Dermatomyositis = skin involvement

Question 2

Who does dermatomyositis affect?

Answer 2

Women > Men

Adult onset >40yrs

Juvenile onset 4-10yrs

Question 3

What is the presenting features of dermatomyositis?

Answer 3

Heliotrope (red / purple colour) rash on eyelids

Photosensitive

Itch

Periorbital oedema

Poikiloderma (reticulate pigmentation, atrophy and telangiectasia)

Periungal redness (dialted capillaries on nail folds/cuticles)

Gottron’s papules (flat violet knuckle papules and over extensor surfaces)

Assoc. with myalgia, polyarthritis and Raynaud’s phenomenon

Question 4

What conditions is dermatomyositis associated with?

Answer 4

SLE, rheumatoid arthritis

Malignancies i.e. lung, breast, ovary, or stomach ca.

Question 5

What investigations are carried out for dermatomyositis?

Answer 5

1. Serum creatinine kinase
   => aminotransferases, lactate dehydrogenase (LDH) raised - muscle damage
2. Raised ESR & CRP
3. Serum autoantibody
   => ANA +ve
   => Rheumatoid factor present in 50%
   => Myositis-specific antibodies (MSAs)
4. Electromyography (EMG)
   => Triad of myositis
   i. spontaneous fibrillation of potentials at rest
   ii. polyphasic or short durations potentials on voluntary contraction
   iii. repetitive potentials on mechanical stimulation of the nerve
5. Needle muscle biopsy
   => fibre necrosis + regeneration
6. MRI
7. Screening for malignancy i.e. CT / PET

Question 6

How is dermatomyositis managed?

Answer 6

Bed rest combine with exercise programme

Prednisolone

Immunosuppressive drugs if relapse i.e. methotrexate, azathioprine, ciclosporin, mycophenolate mofetil