Dermatomyositis

Question 1

what is the definition of DM?

Answer 1

Dermatomyositis (DM) is an idiopathic autoimmune inflammatory disorder characterised by a myopathy with a distinctive cutaneous eruption.

Question 2

what is the epidemiology of DM?

Answer 2

DM occurs in both adult and juvenile forms and can overlap with other connective tissue disorders

Question 3

what is the aetiology of DM?

Answer 3

It may be associated with interstitial lung disease, cardiac involvement, oesophageal involvement, dystrophic calcification, and underlying malignancy. Adult-onset DM is significantly associated with occult malignancy

Question 4

what are the risk factors for DM?

Answer 4

genetic predisposition
bimodal age distribution: children and age >40 years
female sex
black race

Question 5

what are the key presentations of DM?

Answer 5

Skin lesions are frequently the initial presenting complaint, with muscle involvement developing later. Some patients have cutaneous involvement alone. Hallmark features include a heliotrope rash, Gottron’s papules, photosensitivity, and nail fold capillary dilatation.
presence of risk factors
Gottron’s papules
heliotrope rash with or without periorbital oedema
macular violaceous erythema
stiffness

Question 6

what are the symptoms of DM?

Answer 6

photosensitivity
poikiloderma vasculare atrophicans
pruritus
fatigue and malaise

Question 7

what are the first line and gold standard investigations for DM?

Answer 7

Serum creatine kinase 
Serum aldolase
Muscle biopsy 
Electromyogram 
Skin biopsy 
Antinuclear antibody 
myositis -specific antibodies

Question 8

what are the differential diagnoses for DM?

Answer 8

Subacute cutaneous lupus erythematosus (SCLE)
Psoriasis
Cutaneous T-cell lymphoma

Question 9

how is DM managed?

Answer 9

Muscle disease is treated with high-dose oral corticosteroids, followed by the addition of immunosuppressants or intravenous immunoglobulin in refractory cases, rituximab
Skin manifestations are treated with topical antipruritics and topical corticosteroids. Antimalarials and topical tacrolimus can be used in resistant disease
Immunosuppressants and intravenous immunoglobulin are generally used for resistant and severe skin disease. Photoprotection is advised in all patients.