Inflammatory Myositis Flashcards
Dermatomyositis
Overview
inflammatory disorder causing symmetrical, proximal muscle weakness and characteristic skin lesions
may be idiopathic or associated with connective tissue disorders or underlying malignancy (typically lung cancer, found in 20-25% - more if patient older)
polymyositis is a variant of the disease where skin manifestations are not prominent
Dermatomyositis - Skin Features
Skin features
photosensitive
macular rash over back and shoulder
heliotrope rash in the periorbital region
Gottron’s papules - roughened red papules over extensor surfaces of fingers
nail fold capillary dilatation
Dermatomyositis - Other Features
Other features proximal muscle weakness +/- tenderness Raynaud's respiratory muscle weakness interstitial lung disease: e.g. Fibrosing alveolitis or organising pneumonia dysphagia, dysphonia
Dermatomyositis - Diagnosis: Example Question
52 year old female has presented to your neurology clinic reporting difficulty in lifting her arms during exercises at the gym over the past two months. She is distressed by her symptoms and is tearful, mentioning that she is also using significant amounts of make up to cover a new purple rash and swelling around her eyelids. She reports no past medical history no recent trauma and is normally fit and well. She has had a dry cough for the past 5 months that she puts down to her previous social smoking, when she would smoke up to 2 cigarettes when she goes out with friends every 2 weeks.
On examination, you note limited range of passive movement in both shoulders and hips secondary to tender deltoids and hip flexors. Examination of power demonstrates 4- out of 5 symmetrically in hip flexion and shoulder abduction. An elliptical erythematous rash is present around her eyes, the skin around her fingers appear tough bilaterally. Auscultation of her chest reveals bibasal fine inspiratory crackles and normal heart sounds. Observations show she is currently has a low grade temperature of 37.7 degrees. A chest radiograph demonstrates bilateral fibrotic changes.
Her admission blood tests are as follows:
Hb 12.1 g/dl Platelets 590 * 109/l WBC 12.3 * 109/l ESR 20 mm/hr Creatine kinase 3000 u/l LDH 250 u/l
What is the unifying diagnosis?
Inclusion body myositis Systemic sclerosis > Dermatomyositis Polymyalgia rheumatica Fibromyalgia
The patient has presented with a syndrome of proximal myopathy associated with a violaceous rash on her eyelid and mechanics hands, in addition to possible interstitial lung disease. The most suspicious diagnosis is an inflammatory myositis. Inclusion body myositis is a diagnosis of exclusion and is normally isolated to proximal and less commonly distal, bulbar and facial muscles. Systemic sclerosis is a possible diagnosis and can produce inflammatory myositis similar to polymyositis. However, cranial and peripheral neuropathies are more common. The distinctive cutaneous features in this patient are strongly suggestive of dermatomyositis: the violaceous eyelid rash and oedema is a heliotropic rash associated with dermatomyositis. Other cutaneous findings include Gottron’s papules (violaceous papules on the extensor surfaces of fingers), shawl and V sign (photosensitive hyperpigmentation around the shoulders and upper chest), mechanics hands and periungual erythema. Note the normal ESR result, which is often not elevated in dermatomyositis patients.
Polymyositis
Overview
inflammatory disorder causing symmetrical, proximal muscle weakness
thought to be a T-cellmediated cytotoxic process directed against muscle fibres
may be idiopathic or associated with connective tissue disorders
associated with malignancy
dermatomyositis is a variant of the disease where skin manifestations are prominent, for example a purple (heliotrope) rash on the cheeks and eyelids
typically affects middle-aged, female:male 3:1
Polymyositis - Features
Features proximal muscle weakness +/- tenderness Raynaud's respiratory muscle weakness interstitial lung disease: e.g. fibrosing alveolitis or organising pneumonia dysphagia, dysphonia
Polymyositis - Ix
Investigations elevated creatine kinase EMG muscle biopsy anti-Jo-1 antibodies are seen in pattern of disease associated with lung involvement, Raynaud's and fever
Polymyositis - Diagnosis and Ix: Example Question
An 80-year-old retired GP with no past medical history presents to hospital with a 6 month history of muscle aches and weakness. She also has difficulty swallowing and has had 3 courses of antibiotics for a presumed chest infection in the last 3 months. In the last 2 days she has been struggling to cope at home and has had two falls.
Blood tests show :
Erythrocyte Sedimentation Rate (ESR) 60 mm/hour g/l
Creatinine Kinase 8000 U/L
Which of the following blood tests would be LEAST helpful in the work up?
Autoimmune profile FBC AST and ALT Urine myoglobin > Renal biopsy
This lady seems to have polymyositis. An autoimmune profile is useful as ANA is positive in one third of patients. Anti-jo antibodies are positive in 20% of patients and indicate a poorer prognosis with interstitial lung disease. A full blood count may show leukocytosis or thrombocytosis. AST/ALT are both muscle enzymes that will be elevated. Creatinine kinase will also be elevated along with urine myoglobin. In some cases the patient may develop renal impairment from rhabdomyolysis and thus U+Es should be monitored. Renal biopsy would not be diagnostically helpful in this situation.
Dermatomyositis - Ix
Ix
- EMG
- Muscle biopsy
- ANA +ve in 60%
- anti-Mi-2 antibodies are highly specific for dermatomyositis, but are only seen in 25% of patients
- anti-Jo-1 antibodies are not commonly seen in dermatomyositis (more common in polymyositis where they are assoc w lung involvement, Raynaud’s and fever)
Mx = PREDNISOLONE
Dermatomyositis -Cutaneous Features
Distinctive Cutaneous Features:
- the violaceous eyelid rash and oedema is a heliotropic rash associated with dermatomyositis
- Gottron’s papules (violaceous papules on the extensor surfaces of fingers)
- shawl and V sign (photosensitive hyperpigmentation around the shoulders and upper chest)
- mechanics hands
- periungual erythema.
NB Normal ESR result
