Polymyositis and dermatomyositis Flashcards
What are polymyositis and dermatomyositis?
Inflammatory muscle diseases characterised by bilateral proximal muscle weakness
What cancers are dermatomyositis and polymyositis associated with?
Cervical
Lung
Breast
Pancreatic
Ovarian
Gastrointestinal
Non-hodgkin’s lymphoma
What is the presentation of polymyositis?
Symmetrical proximal muscle weakness
Difficulty climbing stairs, lifting objects, and holding up head
Muscle cramps
Dysphagia due to pharyngeal weakness
Systemic symptoms:
- Weight loss
- Fever
- Anorexia
- Fatigue
- Arthralgia
What is the clinical presentation of dermatomyositis?
Same presentation of polymyositis with:
- Heliotrope rash
- Gottron’s papules
- Maculopapular violaceous erythematous rash over shoulders and upper chest/back
- Holster sign - erythema of buttocks
- Rashes are photosensitive
What is a heliotrope rash?
Purple-red rash over the eyelids, forehead and cheeks
May be associated with periorbital oedema
What are Gottron’s papules?
Scaly, erythematus papules over the knuckles and extensor surfaces of the knees and elbows
What are the differentials of polymyositis and dermatomyositis?
Medication induced myopathy
Thyroid disease
Muscular dystrophy
Hypokalaemia
Vitamin D deficiency
Inclusion body myositis
What investigations are performed in the diagnosis of polymyositis and dermatomyositis?
Urinalysis - myoglobinuria
Creatine kinase - raised
Lactate dehydrogenase - raised
Antibody testing
MRI of affected regions
Electromyography - myopathic changes
What antibody is most commonly associated with dermatomyositis?
Anti-Mi-2 antibodies
What antibody is most commonly associated with polymyositis?
Anti-Jo-1 antibodies
What is the conservative management of polymyositis and dermatomyositis?
Specialist physiotherapy
SALT for patients with dysphagia
Sun avoidance and high factor sun cream (Dermatomyositis)
FRAX scoring, with consideration of bone protection
What is the medical management of polymyositis and dermatomyositis?
First line - high dose steroids (oral prednisolone 40-60mg daily)
Steroids should be weaned once disease activity has improved
DMARD should be given alongside steroids
What are the treatment options for refractory myositis?
IVIG
Cyclophosphamide
Rituximab and abatacept
What are the complications of polymyositis and dermatomyositis?
Interstitial pneumonitis
Conduction defects
Arrhythmias
Myocarditis
Weight loss and aspiration pneumonia due to dysphagia
What are poor prognostic factors for polymyositis and dermatomyositis?
Older age
Male gender
Cardiac involvement
Dysphagia
Autoantibodies - anti-TIF1, anti-MDA-5
