eMedicine Specialties > Dermatology > Connective Tissue Diseases

Dermatomyositis: Differential Diagnoses & Workup

Author: Jeffrey P Callen, MD, Professor of Medicine, Chief, Division of Dermatology, University of Louisville School of Medicine
Contributor Information and Disclosures

Updated: Apr 13, 2009

Differential Diagnoses

CREST Syndrome
Parapsoriasis
Graft Versus Host Disease
Pityriasis Rubra Pilaris
Lichen Myxedematosus
Polymorphous Light Eruption
Lichen Planus
Psoriasis, Plaque
Lupus Erythematosus, Acute
Rosacea
Lupus Erythematosus, Discoid
Sarcoidosis
Lupus Erythematosus, Subacute Cutaneous
Tinea Corporis
Morphea
Urticaria, Chronic
Multicentric Reticulohistiocytosis

Workup

Laboratory Studies

  • Muscle enzyme levels are often abnormal at some time in patients with dermatomyositis, except in those with the amyopathic variant. The most common enzyme level to obtain is the creatine kinase level. However, an aldolase level test and other tests, such as aspartate aminotransferase and lactate dehydrogenase tests, may also yield abnormal results. At times, the elevation of the enzyme levels precedes clinical evidence of myositis. Therefore, if a patient who is presumably stable develops an elevation in an enzyme level that was previously normal, the clinician should assess the possibility of a flare of the muscle disease.
  • Several serologic abnormalities have been identified, but their routine use has not yet been delineated. As a group, these antibodies have been termed myositis-specific antibodies (MSAs).
    • A positive antinuclear antibody result is common in patients with dermatomyositis.
    • Anti-Mi-2 is highly specific for dermatomyositis, but it lacks sensitivity because only 25% of patients with dermatomyositis demonstrate this abnormality.
    • Anti-Jo-1 and other antisynthetase antibodies are associated with pulmonary involvement, but it is more common in patients with polymyositis than dermatomyositis.
    • Other MSAs include antisignal recognition protein and anti-Ku.

Imaging Studies

  • MRI with T2 weighting or magnetic resonance spectroscopy may be useful for assessing the presence of an inflammatory myopathy in patients without weakness. It is also useful in differentiating a steroid myopathy from a continued inflammation. Lastly, it may serve as a guide for selection of a site for muscle biopsy.
  • Chest radiography should be obtained at the time of diagnosis and when symptoms develop.
  • The barium swallow test allows evaluation of esophageal dysmotility.
  • Ultrasonography of the muscles has been suggested for evaluation, but its use has not been widely accepted.

Other Tests

  • Pulmonary function studies, including diffusion studies, and electrocardiography may be performed.
  • Esophageal manometry or other esophageal studies may be performed in selected patients.
  • Electromyography is a means of detecting inflammation of the muscles. At times, it has been useful for the selection of a site for muscle biopsy. This test is less commonly obtained now by dermatologists caring for patients with typical skin lesions.

Procedures

  • An age-appropriate evaluation for a possible malignancy should be performed at the time of diagnosis and then annually for the first 3 years. Female patients should be carefully screened for ovarian cancer.18 After that time, patients should be evaluated for malignancy at intervals similar to any other person of the same age and sex.19
  • Muscle biopsy, either open biopsy or needle biopsy, may enhance the ability of the clinician to diagnose dermatomyositis. It is also sometimes useful in differentiating steroid myopathy from active inflammatory myopathy when patients have been on corticosteroid therapy but are still weak.

Histologic Findings

Skin biopsy samples reveal an interface dermatitis that is difficult to differentiate from lupus erythematosus. Often, the histologic features of dermatomyositis and lupus erythematosus are identical. Both may contain excessive mucin, and both demonstrate an interface vacuolar dermatitis. Well-formed lesions of discoid lupus erythematosus differ from those of dermatomyositis, but often dermatomyositis and subacute cutaneous lupus erythematosus cannot be differentiated.20

More on Dermatomyositis

Overview: Dermatomyositis
Differential Diagnoses & Workup: Dermatomyositis
Treatment & Medication: Dermatomyositis
Follow-up: Dermatomyositis
Multimedia: Dermatomyositis
References
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References

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  14. Lutz J, Huwiler KG, Fedczyna T, et al. Increased plasma thrombospondin-1 (TSP-1) levels are associated with the TNF alpha-308A allele in children with juvenile dermatomyositis. Clin Immunol. Jun 2002;103(3 Pt 1):260-3. [Medline].

  15. Werth VP, Callen JP, Ang G, Sullivan KE. Associations of tumor necrosis factor alpha and HLA polymorphisms with adult dermatomyositis: implications for a unique pathogenesis. J Invest Dermatol. Sep 2002;119(3):617-20. [Medline].

  16. Daoud MS, Gibson LE, Pittelkow MR. Hydroxyurea dermopathy: a unique lichenoid eruption complicating long-term therapy with hydroxyurea. J Am Acad Dermatol. Feb 1997;36(2 Pt 1):178-82. [Medline].

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  32. Oliveri MB, Palermo R, Mautalen C, Hubscher O. Regression of calcinosis during diltiazem treatment in juvenile dermatomyositis. J Rheumatol. Dec 1996;23(12):2152-5. [Medline].

  33. Ambler GR, Chaitow J, Rogers M, McDonald DW, Ouvrier RA. Rapid improvement of calcinosis in juvenile dermatomyositis with alendronate therapy. J Rheumatol. Sep 2005;32(9):1837-9. [Medline].

  34. Klein RQ, Bangert CA, Costner M, et al. Comparison of the reliability and validity of outcome instruments for cutaneous dermatomyositis. Br J Dermatol. Sep 2008;159(4):887-94. [Medline].

  35. Marie I, Hatron PY, Levesque H, et al. Influence of age on characteristics of polymyositis and dermatomyositis in adults. Medicine (Baltimore). May 1999;78(3):139-47. [Medline].

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Further Reading

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Keywords

dermatomyositis, idiopathic inflammatory myopathy, dermatomyositis sine myositis, amyopathic dermatomyositis, juvenile dermatomyositis, childhood dermatomyositis, polymyositis, vesiculobullous erosive lesions, exfoliative erythroderma, heliotrope rash, Gottron papules, poikiloderma, calcinosis

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Contributor Information and Disclosures

Author

Jeffrey P Callen, MD, Professor of Medicine, Chief, Division of Dermatology, University of Louisville School of Medicine
Jeffrey P Callen, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and American College of Rheumatology
Disclosure: Amgen Honoraria Consulting; Abbott Honoraria Consulting; Electrical Optical Sciences Honoraria Consulting; Centocor Honoraria Consulting; Genetech Honoraria Consulting; Celgene Honoraria Consulting

Medical Editor

Kathleen David-Bajar, MD, Former Consultant to the Army Surgeon General, Department of Dermatology, Brooke Army Medical Center
Kathleen David-Bajar, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.

Pharmacy Editor

Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Association of Military Dermatologists, Texas Dermatological Society, and Texas Medical Association
Disclosure: Nothing to disclose.

Managing Editor

Jeffrey Meffert, MD, Assistant Clinical Professor of Dermatology, University of Texas Health Science Center-San Antonio
Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, Association of Military Dermatologists, and Texas Dermatological Society
Disclosure: Nothing to disclose.

CME Editor

Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University
Catherine Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.

Chief Editor

William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System
William D James, MD is a member of the following medical societies: American Academy of Dermatology and Society for Investigative Dermatology
Disclosure: elsevier Royalty Other; american college of physicians Honoraria Other

 
 
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