Idiopathic inflammatory myopathies (incl. polymyositis, dermatomyositis) Flashcards
What are Idiopathic inflammatory myopathies?
Connective tissue diseases characterised by insidious onset of progressive symmetrical proximal muscle weakness + AI mediated striated muscle inflammation (myositis) associated with myalgia +/- arthralgia
What is myalgia?
Muscle pain
What is Arthralgia?
Joint pain
Describe the aetiology of Idiopathic inflammatory myopathies
AI basis
Viral infection implicated in its pathogenesis e.g. influenza, EBV
Dermatomyositis features myositis plus skin changes
Describe the epidemiology of Idiopathic inflammatory myopathies
RARE
Polymyositis: 30-60 yrs
Dermatomyositis: any age (peaks: 5-10 + 50)
F > M
List 6 presenting symptoms/ features of polymyositis
Diffuse weakness in proximal muscles Distal muscles spared (fine motor coordination preserved in early stages) Pharyngeal weakness: Dysphagia Dysphonia Respiratory weakness: SOB NO rash
What may diffuse weakness in proximal muscles in polymyositis cause?
Difficulty rising from a low chair, climbing steps, lifting objects + combing hair
Fatigue
Myalgia
Muscle cramps
List 6 features of dermatomyositis
RASH
Systemic upset with fever, arthralgia, malaise + weight loss
Possible cardiac disease (e.g. conduction blocks, tachyarrhythmia)
GI ulcers + infections
Interstitial lung disease (30-50%)
Children have more non-muscular features (e.g. GI ulcers + infections)
List 8 signs of polymyositis
Fever Muscle weakness NOT painful in most Proximal myopathy Extraocular muscles + distal muscles spared Weak forced flexion of the neck Muscular atrophy Muscles may be tender on palpation
List 6 signs of dermatomyositis
Macular rash
Nailfold erythema
Gottron’s papules: roughened red papules over knuckles, elbows + knees
Proximal myopathy
Muscle pain + tenderness in early disease
Fever
Describe the rash seen in dermatomyositis
Shawl sign = rash over back + shoulders
Lilac-purple heliotrope rash on eyelids often with oedema
May affect knees, shoulders, back + upper arms
May be exacerbated by sunlight
What 5 investigations may be performed for polymyositis?
Creatine kinase: up to 50 x higher than normal Electromyography (EMG) Muscle biopsy Autoantibodies Enzymes
What is the definitive test for polymyositis?
Muscle biopsy
What autoantibodies may be seen in polymyositis?
Myositis specific antibody
Anti-Jo-1 antibody
What 4 investigations may be performed for dermatomyositis?
Creatine kinase: not as reliable as in polymyositis
Enzymes
Autoantibodies
EMG: may be normal as well
