Dermatomyositis/Polymyositis
Dermatomyositis/Polymyositis: Excerpt from The 5-Minute Pediatric Consult
Randy Q. Cron, MD, PhD
Dermatomyositis/Polymyositis - BASICS
Dermatomyositis/Polymyositis - description
The dermatomyositis/polymyositis complex includes a number of conditions in which muscle becomes damaged by a nonsuppurative lymphocytic inflammatory process. Juvenile dermatomyositis (JDM) is the most common seen in the pediatric population.
Dermatomyositis/Polymyositis - epidemiology
- The average age of onset is 7 years.
- Overall male/female ratio is 1:1.7; however, equal in children <10 years of age
Dermatomyositis/Polymyositis - incidence
1:200,000
Dermatomyositis/Polymyositis - genetics
HLA-DQ0301
Dermatomyositis/Polymyositis - etiology
- Unknown
- Several potential mechanisms include:
- Abnormal cell-mediated immunity
- Immune-complex formation
- Immunodeficiency
- Infection
- Microchimerism
Dermatomyositis/Polymyositis - DIAGNOSIS
Dermatomyositis/Polymyositis - signs & symptoms
Diagnosis requires the presence of the pathognomonic rash plus 3 additional criteria:
- Progressive symmetric weakness of proximal muscles
- Dermatitis-heliotrope rash over eyelids, Gottron papules over extensor surfaces of joints
- Elevated serum level of muscle enzymes
- Electromyograph (EMG) findings of myopathy and denervation
- Biopsy demonstration of inflammatory myositis
- Although not a criterion, T2-weighted magnetic resonance imaging is useful in establishing active myositis.
Dermatomyositis/Polymyositis - history
- Fever: Evidence of systemic illness
- Anorexia and weight loss: GI involvement
- Fatigue: Sign of muscle weakness
- Weakness: Difficulty rising from floor, climbing stairs, swallowing, regurgitation through nose
- Dysphonia: Sign of muscle weakness
- Rash could contain clue to diagnosis.
Dermatomyositis/Polymyositis - physical exam
- Muscle weakness: Proximal and symmetric tenderness strength
- Rash:
- 75% have pathognomonic rash, which usually appears several weeks after muscle weakness
- Facial rash:
- Violaceous, heliotropic changes over eyelids
- Extremities:
- Gottron papules over extensor surfaces
- Nailfold telangiectasia:
- Simultaneous dilated loops, dropout, and arborized capillary loops
- Physical examination tricks:
- Gower sign: Inability to rise from floor without using hands
- Use ophthalmoscope to examine nailfold for telangiectasia.
- Objective measure of strength: Duration of straight leg raise (normal = 20 seconds)
Dermatomyositis/Polymyositis - tests
Dermatomyositis/Polymyositis - lab
- Autoantibodies:
- Normal rheumatoid factor, complement, and double-stranded DNA (dsDNA)
- Antinuclear antibody: 10–50%
- PM-1: 60% adult polymyositis; however, rare in children
- Jo-1: Associated with interstitial lung disease
- Muscle enzymes:
- Elevated in 95% cases
- Creatine kinase
- Aspartate aminotransferase
- Aldolase
- Lactate dehydrogenase
Dermatomyositis/Polymyositis - imaging
- MRI:
- Inflamed muscles are identified by signal enhancement.
- Useful to direct biopsy
- Barium swallow:
- To identify palatal or proximal esophageal weakness
- Pulmonary function tests/peak flow:
- To evaluate pulmonary musculature and interstitial lung disease
Dermatomyositis/Polymyositis - pathological findings
- Skeletal muscle:
- Group atrophy or perifascicular myopathy
- Variation in fiber size owing to concomitant degeneration and regeneration
- Inflammatory exudate in perivascular distribution
- Necrotizing vasculitis of arterioles, capillaries, and venules; probably owing to immune complex deposition
- Skin:
- Epidermal atrophy
- Vascular dilatation
- Lymphocyte infiltration of the dermis
Dermatomyositis/Polymyositis - differencial diagnosis
- Postinfectious:
- Influenza A and B, coxsackievirus B, schistosomiasis, trypanosomiasis, toxoplasmosis
- Bacterial/pyomyositis-focal
- Myositis with other connective tissue diseases:
- Overlap with juvenile rheumatoid arthritis
- Mixed connective tissue disease
- Systemic lupus erythematosus
- Childhood neuromuscular diseases:
- If no rash, consider: Muscular dystrophy; congenital myopathies; metabolic disorders (glycogen storage disease, carnitine deficiency, myoadenylate deaminase)
- Neurogenic atrophies (spinal muscular atrophy and anterior horn, peripheral nerve dysfunction)
- Neuromuscular transmission disorders
- Inclusion body myositis
Dermatomyositis/Polymyositis - TREATMENT
Dermatomyositis/Polymyositis - general measures
Supportive care:
- Monitor for swallowing difficulty.
- Respiratory compromise occasionally requires mechanical ventilation.
- Treatment of calcinosis may include colchicine, diltiazem, and alendronate, but most are generally ineffective.
Dermatomyositis/Polymyositis - phys therapy
- Initially to maintain range of movement
- Strengthening only after acute inflammation resolves
Dermatomyositis/Polymyositis - medication
- 2 mg/kg of steroids per day for 1 month, taper over months to years
- IV gamma globulin, controversial, efficacious for rash
- Plaquenil, particularly useful for the rash
- Methotrexate (PO, SC, or IV, avoid IM), which may alter serum levels of muscle enzymes
- Cyclosporine
- Steroid-induced myopathy
- Insidious onset
- Proximal and distal muscles, often large muscle groups such as hip flexors
- Normal serum muscle enzymes
- Minimal myopathic changes on electromyograph
- Type II fiber atrophy on muscle biopsy
Dermatomyositis/Polymyositis - FOLLOW UP
Dermatomyositis/Polymyositis - prognosis
- Normal to good: 65–80%
- Minimal atrophy and joint contractures: 24%
- Calcinosis: 20–40%
- Wheelchair dependent: 5%
- Death: 7–10%
Dermatomyositis/Polymyositis - complications
- Myositis
- Rash
- Arthritis
- Calcinosis
- Raynaud syndrome
- Dysphagia and dysphonia
- Restrictive lung disease and aspiration pneumonia
- Myocarditis (rare)
- GI tract vasculitis
- Osteoporosis
- Joint contractures
- Skin infections
Dermatomyositis/Polymyositis - patient monitoring
- Function
- Muscle strength
- Joint range of movement
- Development of calcinosis
- Muscle enzyme levels
Dermatomyositis/Polymyositis - bibliography
- Huber A, Feldman BM. Long-term outcomes in juvenile dermatomyositis: How did we get here and where are we going? Curr Rheumatol Rep. 2005;7:441–446.
- Lindsley CB. Juvenile dermatomyositis update. Curr Rheumatol Rep. 2006;8:174–177.
- Mamyrova G, O’Hanlon TP, Monroe JB, et al. Immunogenetic risk and protective factors for juvenile dermatomyositis in Caucasians. Arthritis Rheum. 2006;54:3979–3987.
- Pachman LM, Abbott K, Sinacore JM, et al. Duration of illness is an important variable for untreated children with juvenile dermatomyositis. J Pediatr. 2006;148:247–253.
- Reed AM. Microchimerism in children with rheumatic disorders: What does it mean? Curr Rheumatol Rep. 2003;5:458–462.
Dermatomyositis/Polymyositis - CODES
Dermatomyositis/Polymyositis - icd9
710.3 Dermatomyositis
Dermatomyositis/Polymyositis - FAQ
- Q: Is it mandatory to perform a muscle biopsy to confirm the diagnosis?
- A: No.
- Q: Is there an associated risk of malignancy as for adults with this disorder?
- A: Extremely rare.
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Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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