Polymyositis And Dermatomyositis Flashcards
Define polymyositis and dermatomyositis?
Connective tissue diseases characterised by inflammation of muscles
What is the aetiology of polymyositis and dermatomyositis?
Autoimmune basis
Viral infection has been implicated in its pathogenesis
What is the epidemiology of polymyositis and dermatomyositis?
Polymyositis presents between 30-60 yrs
Dermatomyositis can occur at any age (peak onset: 5-10 (children) and 50 (adults))
Both diseases are 2 x more common in FEMALES
What are the presenting symptoms of Polymyositis?
Inflammatory myopathy with onset over weeks or months Steady progression of symptoms Diffuse weakness in proxiumal muscles Distal muscles are spared Pharyngeal weakness No rash
What does diffuse weakness in proximal muscles result in for Polymyositis?
Causing difficulty rising from a low chair, climbing steps, lifting objects and combing hair
Also fatigue, myalgia and muscle cramps
What is the result of Distal muscles being spared in Polymyositis?
Fine motor coordination tends to be preserved in the early stages
What can pharyngeal weakness lead to in Polymyositis?
Dysphagia
What are the presenting symptoms of Dermatomyositis?
Inflammatory myopathy with onset over weeks or months
RASH
Systemic upset with fever, arthralgia, malaise and weight loss
Possible cardiac disease (e.g. conduction blocks, tachyarrhythmia)
GI ulcers and infections
Interstital lung diseases (30-50%)
Children have more non-muscular features (e.g. GI ulcers and infectiosn)
What are the signs of Polymyositis on physical examination?
Muscle Weakness NOT painful in most patients Proximal myopathy Extraocular muscles and distal muscles are spared Weak forced flexion of the neck Muscular atrophy Muscles may be tender on palpation
What are the signs of Dermatomyositis on physical examination?
RASH characteristics
Rash may affect knees, shoulders, back and upper arms
Rash may be exacerbated by sunlight
Proximal myopathy
Muscle pain and tenderness in early disease
What are the RASH characteristics you see in Dermatomyositis?
Blue-purple discolouration of the upper eyelids with periorbital oedema
Flat red rash involving the face and upper trunk
Raised purple-red scaly patches over the extensor surfaces of joints and fingers
What investigations would you do for Polymyositis?
Creatine Kinase - up to 50x higher than normal
Electromyography (EMG)
Muscle biopsy - DEFINITIVE TEST
Autoantibodies (e.g. myositis specific antibody, anti-Jo-1 antibody
Enzymes (e.g. SGOT, SGPT, LDH)
What investigations do you do for Dermatomyositis?
Creatine kinase - not as reliable as in polymyositis
Enzymes (SGOT, SGPT and LDH may be raised)
Autoantibodies
EMG - may be helpful but can be normal as well
Muscle biopsy
What autoantibodies do we do to investigate Dermatomyositis?
ANA
Anti-Mi-2
Anti-Jo-1 (more common in polymyositis)
