Rosen & Barkin's 5-Minute Emergency Medicine Consult (202 page)

• Although DM is seen in both children and adults, PM is rare in children
  
• Similar to adult DM, juvenile DM (JDM) primarily affects the skin and skeletal muscles
  
• Juvenile form may include vasculitis, ectopic calcifications (calcinosis cutis), and lipodystrophy
  
• The juvenile form may be associated with coxsackievirus
  

DIAGNOSIS

• PM is distinguished from DM by the absence of rash
  
• Patients with PM present with muscle pain and proximal muscle weakness
  
• DM presents with skin rash, muscle pain, and weakness
  
• Constitutional symptoms include weight loss, fever, anorexia, morning stiffness, myalgias, and arthralgias
  
• Patients often note fatigue doing customary tasks:
  
  • Brushing hair, climbing stairs, reaching above the head, rising from a chair
    
  • May also complain of dysphagia, dyspnea, and cough
    
• Progressive weakness of the proximal limb and girdle muscles is seen early; distal muscle weakness can occur late in the disease
  

• General:
  
  • Fatigue
    
  • Fever
    
  • Weight loss
    
• Dysphagia
  
• Progressive muscle weakness:
  
  • Involves proximal muscles primarily
    
  • Symmetrical
    
• Skin findings of DM:
  
  • Skin rash occurs with or precedes muscle weakness
    
  • Heliotrope rash (lilac discoloration) on the upper eyelids associated with edema
    
  • Gottron sign: Violaceous or erythematous papules over the extensor surfaces of the joints, particularly knuckles, knees, and elbows
    
  • Shawl sign: A V-shaped erythematous rash occurring on the back and shoulders
    
  • Periungual telangiectasias: Nail-bed capillary changes that include thickened irregular and distorted cuticles
    
  • “Machinist hands”: Darkened horizontal lines across the lateral and palmar aspects of the fingers
    

• Assess airway and breathing for any signs of aspiration or compromise
  
• Assess for any signs of cardiac involvement and complications
  

• Serum muscle enzymes:
  
  • Creatine phosphokinase (CPK) is elevated, other muscle enzymes such as aldolase, can also be elevated
    
• Diagnostic criteria established in 1975 by Bohan and Peter:
  
  • Symmetric proximal muscle weakness with dysphagia and respiratory muscle weakness
    
  • Elevation of serum muscle enzymes
    
  • Electromyographic features of myopathy
    
  • Muscle biopsy showing features of inflammatory myopathy
    
  • Confidence limits for diagnosis (typical rash must be seen for diagnosis of DM):
    
    • Definite diagnosis: 3 or 4 criteria
      
    • Probable diagnosis: 2 criteria
      
    • Possible diagnosis: 1 criterion
      
• Newer diagnostic criteria using autoantibody profiles (Anti-Jo-1, Anti-SRP, Anti-Mi-2) or immunohistologic characterization may prove to be more specific for diagnosis of specific disease subgroups
  

• Chest radiograph may show interstitial lung disease, evidence of aspiration pneumonia, CHF, or cardiomyopathy
  
• EMG studies show myopathic potentials that may support the diagnosis but are not specific for DM/PM
  
• Increasing role for MRI in determining regions of inflammation best suited for biopsy
  

• Muscle biopsy is the definitive test:
  
  • In PM, inflammatory infiltrates are often endomysial, although they may be perivascular
    
  • In DM, inflammatory infiltrates are mostly perivascular and include a high percentage of B cells
    
• Renal biopsies of patients may show focal proliferative glomerulonephritis
  
• Pulmonary function tests are useful in following the progression of interstitial lung disease
  

• Collagen vascular diseases
  
• Muscular dystrophies
  
• Spinal muscular atrophy
  
• Myasthenia gravis
  
• Amyotrophic lateral sclerosis
  
• Poliomyelitis
  
• Guillain–Barré syndrome
  
• Hypothyroidism
  
• Hyperthyroidism
  
• Cushing syndrome
  
• Drug-induced:
  
  • Colchicine
    
  • Zidovudine (AZT)
    
  • Penicillamine
    
  • Ipecac
    
  • Ethanol
    
  • Chloroquine
    
  • Corticosteroids
    
• Infection:
  
  • Toxoplasmosis
    
  • Trichinosis
    
  • Coxsackievirus
    
  • HIV, influenza
    
  • Epstein–Barr virus
    
• Electrolyte disturbances:
  
  • Hypokalemia
    
  • Hypercalcemia
    
  • Hypomagnesemia
    
• Vasculitis
  
• Paraneoplastic neuromyopathy
  
• Hypereosinophilic myalgia syndrome
  

TREATMENT

• Assess ABCs
  
• Transport with elevation of head of bed
  

• Intubation and mechanical ventilation as required
  
• Nasogastric (NG) suction to prevent aspiration
  
• Pneumothorax has been described as a rare occurrence in childhood DM
  

• Elevate head of the bed to prevent aspiration
  
• Begin high-dose corticosteroids to suppress inflammation and improve muscle weakness
  
• Avoid triamcinolone and dexamethasone because they may cause a drug-associated myopathy
  
• Efficacy of prednisone determined by objective increase in muscle strength, not change in CK levels
  
• Some clinicians start glucocorticoid sparing immunosuppressive medications at onset, others reserve these agents for failure to respond to corticosteroids
  
• Azathioprine and methotrexate are used with limitations based on side-effect profiles
  
• Cyclosporine and monoclonal antibody therapies have been used but with limited success
  
• Do not base treatment decisions solely upon CPK level
  

• Prednisone: 60 mg/d PO (peds: 1–2 mg/kg/d PO) (in severe illness consider methylprednisolone pulse 1,000 mg/d for 3 days):
  
  • Length of treatment and taper individualized to clinical response and normalization of CK
    

• Methotrexate: 15–25 mg PO per week (peds: 15 mg/m
  ²
  /wk PO not >25 mg)
  
• Azathioprine: Start at 50 mg/d then in 2 wk, increase by 50 mg until a dose of 1.5 mg/kg/d.
  
  • After 3 mo, may increase dose to 2.5 mg/kg/d if tolerated
    
• Intravenous immunoglobulin (IVIG), plasmapheresis, and cyclosporine are also used by some rheumatologists
  

FOLLOW-UP

• Respiratory insufficiency
  
• Aspiration pneumonia
  
• Profound muscle weakness
  
• Weakened cough mechanisms
  
• Pharyngeal dysfunction
  
• CHF
  

• Well-appearing patients with no respiratory dysfunction and no risk for aspiration
  
• Patients who can take oral corticosteroids and immunosuppressive agents as outpatients
  

Consultation with a rheumatologist should be made when the diagnosis is suspected for assistance with definitive diagnosis and further treatment.

• Compared to the general population, the incidence of malignant conditions appears to be increased in patients with DM (but not in those with PM)
  
• A complete annual physical exam with pelvic, breast, and rectal exams; urinalysis; CBC; blood chemistry tests; and a chest film are often recommended for cancer surveillance in patients with a history of DM
  

• The diagnosis of an inflammatory myopathy is largely clinical supported by selected lab testing and muscle biopsy
  
• Most patients improve with therapy, and many make a full functional recovery, which is often sustained with maintenance therapy
  
• Up to 30% may be left with some residual muscle weakness
  
• It is important to keep in mind that relapses may occur at any time despite successful response to therapy
  

• Amato AA, Barohn RJ. Evaluation and treatment of inflammatory myopathies.
  J Neurol Neurosurg Psychiatry
  . 2009;80:1060–1068.
  
• Casciola-Rosen L, Mammen AL. Myositis autoantibodies.
  Curr Opin Rheumatol
  . 2012;24:602–608.
  
• Gordon PA, Winer JB, Hoogendijk JE, et al. Immunosuppressant and immunomodulatory treatment for dermatomyositis and polymyositis.
  Cochrane Database Syst Rev
  . 2012;8:CD003643.
  
• Longo DL, Kasper DL, Jameson JL, et al. Polymyositis, dermatomyositis, and inclusion body myositis:
  Introduction. In
  Harrison’s Principles of Internal Medicine.
  18th
  ed. New York, FY: McGraw-Hill;
  2012:2103–2103.
  
• Wedderburn LR, Rider LG. Juvenile dermatomyositis: New developments in pathogenesis, assessment and treatment.
  Best Pract Res Clin Rheumatol.
  2009;23:665–678.
  

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