Dermatomyositis

Background
  • Inflammatory myopathy with skin manifestations
  • Affects proximal muscles > distal
  • Female:Male; 2:1
  • Peak incidence 40-50s
  • Juvenille dermatomyositis: 5-10 years of age

Clinical Features
Heliotrope rash

Muscular
  • Symmetric weakness
  • Proximal greater than distal weakness
    • Deltoid and hip flexors
    • difficulty standing from a chair
  • Onset over months
  • Mild myalgias
  • Dysphagia due to esophageal muscle dysfunction
  • GERD due to smooth muscle inflammation, gastric ulcer disease
  • Thoracic muscle weakness

Dermatologic
  • Heliotrope rash on face scalp
  • Periorbital edema
  • Gottron's papules (rash on MCP, PIP, and DIP joints)
  • Shawl sign (rash above shoulders)
  • Pruritus
  • Calcinosis
    • Nodules over joints can lead to debilitating contractures, especially in children

Respiratory
  • Respiratory manifestations associated with presence of anti-Jo1 antibody[1]
    • Increased risk of aspiration, which is a leading cause of death in patients with restricted mobility[2]
  • Poor prognosis
  • Interstitial lung disease
  • Thoracic muscle weakness

Cardiac
  • Dilated cardiomyopathy
  • Cardiac myositis
    • Suspect in known dermatomyositis with mild rhythm disturbances, CHF or myocardial fibrosis
    • Causes include reentry pathways, fibrosis, altered automaticity, conduction system injury or treatment side effects

Other
  • Fever, malaise, fatigue, weight loss
  • High association with malignancy

Differential Diagnosis

Myalgia

Weakness

Evaluation
  • Evaluate for emergent complications (e.g. respiratory distress, cardiomyopathy, arrhythmia)
  • BMP
  • ECG, troponin to screen for myocardial involvement
  • CK, Urinalysis for myoglobin
  • Signs of systemic inflammation[3]
    • ESR elevated in 50% of patients, does not correlate with disease activity
    • Elevated CRP

Non-ED Evaluation
  • ANA, Anti-Jo-1
  • Bedside PFTs (FEV1 and FVC)
  • EMG or muscle biopsy showing myositis
  • Malignancy screening/evaluation
    • Increased risk of malignancy (~30%), especially:[4] ovarian, lung, pancreatic, stomach, colorectal, bladder, and non-hodgkin lymphoma
    • Associated with increased age, male gender and elevated creatinine kinase levels

Management

Mild disease
  • Prednisone 1mg/kg/day (up to 80mg/day)
    • Taper after 6-8 weeks

Severe disease

Outpatient

Disposition
  • Admit for decompensated respiratory, cardiac, or other major disease

See Also

References
  1. Vymetal J, Skacelova M, Smrzova A, Klicova A, Schubertova M, Horak P, Zadrazil J. Emergency situations in rheumatology with a focus on systemic autoimmune diseases. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2016 Mar;160(1):20-9. doi: 10.5507/bp.2016.002. Epub 2016 Feb 10. Review. PubMed PMID: 26868300.
  2. Fujisawa T, Hozumi H, Kono M, Enomoto N, Hashimoto D, Nakamura Y, Inui N, Yokomura K, Koshimizu N, Toyoshima M, Shirai T, Yasuda K, Hayakawa H, Suda T. Prognostic factors for myositis-associated interstitial lung disease. PLoS One [serial on the internet] 2014 Jun [cited 2014 Oct 20]; Available from: http://www.ncbi.nlm.nih.gov/ pmc/articles/PMC4048238/?report=classic
  3. Koler RA and Montemarano A. Dermatomyositis. Am Fam Physician. 2001 Nov 1;64(9):1565-1573.
  4. Hill CL et al. Frequency of specific cancer types in dermatomyositis and polymyositis: a population-based study. Lancet. 2001 Jan 13;357(9250):96-100.
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