Core Dermatology Diagnoses / CategoriesInflammatory

Dermatomyositis

Author: Faculty Reviewer: Resident Reviewer:

Publish date: Posted on
Last updated: May 31, 2022

Keywords #

dermatomyositis
Gottron’s papules
myositis
heliotrope rash
shawl sign

Diagnosis #

Dermatomyositis (DM) is an idiopathic inflammatory myopathy disease with characteristic cutaneous findings and possible pulmonary involvement. It has a bimodal age distribution, affecting adults and children. An estimated 25% of patients with DM have or will develop an associated malignancy, and the risk appears to remain elevated for 3-5 years from disease onset.[1] Malignancy may occur before, concurrent to, or after the presentation of DM. Underlying malignancy is more common in patients greater than 50 years of age. Childhood dermatomyositis is not associated with an increased risk of malignancy.

Key Concepts #
  • Classic skin findings in DM include the shawl sign, heliotrope rash, and Gottron’s papules.
  • DM myopathy typically presents with progressive, symmetrical proximal muscle weakness and associated elevations in serum muscle enzymes.
  • DM may be associated with underlying malignancy. Aggressive malignancy screening is recommended for all adult patients during the first 3-4 years from disease onset.
  • The initial treatment for myopathy is systemic corticosteroids.
  • Immunomodulating and/or non-steroidal immunosuppressive therapies are often required and are first-line systemic treatments for cutaneous disease.
Epidemiology #

The incidence of classic DM is 9.63/1 million people, while the incidence of the amyopathic form is 2.08/million.[2] DM is 2-3 times more common in women than in men.[3 DM has a bimodal age distribution. Adult onset is most common in those aged 50–70 years, while children are age 5-10 years.[3,4]

Clinical Features #

[1,3-5]

  1. Cutaneous findings: May precede and/or persist after the onset of myopathic symptoms. Intense pruritus may be a major symptom.
    1. Heliotrope rash – violaceous rash of the eyelids/periorbital skin, in a symmetrical distribution, with or without accompanying periorbital edema; can manifest as just slight discoloration.
    2. Gottron’s papules: violaceous to erythematous, flat-topped, slightly raised papules overlying bony prominences, especially the knuckles.[1]
    3. Periungual changes: erythema, dilated proximal nailfold capillary loops, ragged cuticles, cuticular hemorrhage and/or hypertrophy.
    4. Violaceous erythema on extensor surfaces.
    5. Scalp features: erythematous psoriasiform dermatitis, can be particularly scaly; non-scarring alopecia.
    6. Poikiloderma: atrophic skin with dilated blood vessels and dyspigmentation.
      1. Typically occurs in a photosensitive distribution – Approximately 50% of patients with DM experience photosensitivity.[6]
        1. “shawl sign” = symmetrical, violaceous erythema distributed across the nape of the neck, posterior aspects of the shoulders and upper back.
        2. “V-neck sign” –involvement of the anterior chest and neck, extensor surfaces of the arm.
      2. Holster sign: poikiloderma or violaceous erythema on lateral aspect of the thighs (not photosensitive).
    7. Facial erythema – malar area often involving the nasolabial folds, forehead, temples.[6]
    8. Hyperkeratosis, scaling, and fissuring of the palms and fingers.
      1. Known as “mechanics hands.”[1]
      2. Associated with anti-synthetase antibodies.[6]
    9. Other, less common cutaneous symptoms include exfoliative erythroderma, vesiculobullous presentations, panniculitis, and ulcerations/erosive lesions.[1]
  2. Muscle: inflammatory myopathy
    1. DM generally affects the proximal muscles in a symmetric distribution and slowly progresses.
      1. May manifest as weakness, difficulty or inability to climb stairs, raise arms above the head, comb hair, rise from a squat or sitting.
      2. Myalgias can occur, with variable tenderness of muscles (though not a typical feature).
      3. Severe muscle weakness can result in respiratory failure.
      4. Involvement of striated muscle of upper GI system leading to dysphagia, dysphonia (may signify a rapid course and poor prognosis).
      5. Distal dysphagia – more common in cases that overlap with another collagen-vascular disorder, scleroderma.[1]
      6. Involvement of cardiac muscle (rare) may result in heart failure.
    2. Amyotrophic form of DM– no muscle weakness, normal muscle enzyme levels.
      1. Defined as the lack of myositis for 6 months in absence of steroid or other immunosuppressive therapies.[4]
  3. Systemic & Other:
    1. Malaise, fatigue, weight loss, low grade fever
    2. Raynaud’s phenomenon
    3. Calcinosis – more common in children and adolescents with DM[4]
    4. Arthritis, arthralgias – swollen, tender joints; morning stiffness
    5. Pulmonary disease – interstitial lung disease in up to 30% of dermatomyositis patients[1]
    6. Cardiac involvement5 – arrhythmias, MI, pericarditis
Differential Diagnoses #
  • Cutaneous features: subacute cutaneous lupus erythematous (SCLE), systemic lupus erythematous (SLE), tinea corporis, pityriasis rubra pilaris (PRP), discoid lupus erythematous
  • Scalp involvement can mimic seborrheic dermatitis, psoriasis
  • Gottron’s papules may resemble lichen planus, psoriasis, SCLE, flat warts
  • Drug-induced dermatomyositis: hydroxyurea, quinidine, NSAIDS, and penicillamine have been linked[1,7]
  • Myopathy: rule out infections, toxins, metabolic abnormalities, other neurological disorders and myopathies such as amyotrophic lateral sclerosis, muscular dystrophy, myasthenia gravis, Lambert-Eaton syndrome, drug-induced myopathy
Diagnostic Workup #

Diagnosis of DM is made through a combination of the patient’s history, physical exam, laboratory studies, biopsies, and imaging. In a patient with the cutaneous findings of DM, investigation for concurrent muscle disease should be initiated. Muscle exam and serum muscle enzymes levels should be evaluated approximately every 3 months initially.

  1. ESR, CRP
  2. Muscle enzyme levels
    1. creatine phosphokinase, aldolase, aspartate aminotransferase, lactic dehydrogenase
  3. Skin biopsy of the rash
    1. typically reveals interface dermatitis similar to acute SLE
  4. Antibody panels:
    1. Myositis-specific antibodies:
      1. Detectable in ~ 20-40% of DM or polymyositis cases
      2. Specificity of 90% and are associated with distinct phenotypes[6,7]
      3. Anti-Mi-2, anti-MDA5, anti-TIF, anti-SAE, and anti-NXP are dermatomyositis-specific antibodies
    2. Myositis-associated antibodies:
      1. not disease specific; are often seen in overlap syndromes
    3. Antinuclear (ANA) antibody titers:
      1. commonly positive in patients with DM, although it is not required for diagnosis
  5. Imaging: may vary according to the patient and their symptoms
    1. MRI
    2. CXR
    3. Barium Swallow
    4. Electromyography
  6. Biopsy of an affected muscle may be performed in patients with clinical signs of myositis but in whom noninvasive testing has been negative.
  7. Assessment for pulmonary, esophageal involvement: PFTs, EGD, barium swallow, chest CT
  8. Assessment for underlying malignant disease should be done in all patients, with focus guided by the patients age, sex, and risk factors. Assessment is repeated each year for the first 3 years after diagnosis or if new symptoms develop.[1]
    1. i.e: CT scan of chest, abdomen, pelvis (or PET scan); colonoscopy, Pap smear, CA-125 and CA-19-9, mammogram, transvaginal U/S, PSA, fecal occult blood testing
Treatment #

The first-line treatment for myositis in DM is oral glucocorticoids. However, there are few randomized, placebo-controlled clinical trials and thus no consensus on the dosing, length of treatment, taper speed, or when to add additional therapy.8 In patients with inadequate responses to steroids or with symptom flares during steroid tapers, additional immunosuppressive agents should be added – such as methotrexate, azathioprine, mycophenolate mofetil, tacrolimus, IVIG, rituximab, cyclophosphamide, and cyclosporine.9 In patients who have disease refractory to standard treatment, biologic therapies and immunomodulatory therapies, such as abatacept (Antit-CTLA4 MAb), ruxolitinib & tofacitinib (Jak inhibitors), infliximab (TNF-alpha inhibitor), and apremilast (PDE-4 Inhibitor), among others, may be considered.10

Photoprotection, treatment of pruritus and topical therapy (calcineurin inhibitors, corticosteroids) are the mainstays in management of cutaneous DM. At least 50% of patients with dermatomyositis have photosensitivity, and aggressive sun protection is indicated. Anti-malarial drugs such as hydroxychloroquine have shown benefit in treating cutaneous and constitutional symptoms. For patients with cutaneous disease recalcitrant to these measures, systemic non-glucocorticoid immunosuppressive therapies may be used as in the treatment of myositis (above).

References #
  1. Callen JP. Dermatomyositis. Lancet. 2000;355(9197):53-57.
  2. Bendewald MJ, Wetter DA, Li X, Davis MD. Incidence of dermatomyositis and clinically amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch Dermatol. 2010;146(1):26-30.
  3. Bohan A, Peter JB. Polymyositis and dermatomyositis (first of two parts). N Engl J Med. 1975;292(7):344-347.
  4. Cheeti A, Panginikkod S. Dermatomyositis And Polymyositis. In: StatPearls. Treasure Island (FL): StatPearls Publishing LLC.; 2019.
  5. Köhler S, Carmody L, Vasilevsky N, et al. Expansion of the Human Phenotype Ontology (HPO) knowledge base and resources. Nucleic Acids Research. 2018;47(D1):D1018-D1027.
  6. Muro Y, Sugiura K, Akiyama M. Cutaneous Manifestations in Dermatomyositis: Key Clinical and Serological Features-a Comprehensive Review. Clin Rev Allergy Immunol. 2016;51(3):293-302.
  7. Fernia AN. Dermatomyositis. Medscape. 2018. Published September 26, 2018. Accessed September 23, 2019.
  8. Isak V, Jorizzo JL. Recent developments on treatment strategies and the prognosis of dermatomyositis: a review. J Dermatolog Treat. 2018;29(5):450-459.
  9. Galimberti F, Kooistra L, Li Y, Chatterjee S, Fernandez AP. Intravenous immunoglobulin is an effective treatment for refractory cutaneous dermatomyositis. Clin Exp Dermatol. 2018;43(8):906-912.
  10. Chen KL, Zeidi M, Werth VP. Recent Advances in Pharmacological Treatments of Adult Dermatomyositis. Curr Rheumatol Rep. 2019;21(10):53.
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