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Dermatomyositis. Emily O. Jenkins MD AM Report 9.2.09. Dermatomyositis. Hematoxylin and eosin stain (20x) of a muscle biopsy from a patient with dermatomyositis showing perivascular and perimysial inflammation, as well as perifascicular necrosis. Inflammatory myopathy

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Emily O. Jenkins MD

AM Report



Hematoxylin and eosin stain (20x) of a muscle biopsy from a patient with dermatomyositis showing perivascular and perimysial inflammation, as well as perifascicular necrosis.

  • Inflammatory myopathy

    • Prevalence: 1:100,000 in general population

    • Female to male prevalence of 2:1

    • peak incidence ages 40-50

    • Immune complex deposition in the vessels considered to be part of a complement-mediated vasculopathy

Diagnostic criteria
Diagnostic Criteria

  • Bohan and Peter Criteria:

    • Symmetric proximal muscle weakness

      • most common symptom

    • typical rash

    • elevated serum muscle enzymes

    • myopathic changes on EMG

    • characteristic muscle biopsy abnormalities and absence of histopathologic signs of other myopathies

Signs and symptoms
Signs and Symptoms

  • Grotton’s Sign:

    • An erythematous, scaly eruption over the extensor surfaces of the metacarpophalangeal joints and digits

    • can mimic psoriasis

Signs and symptoms1
Signs and Symptoms

  • Heliotrope rash:

    • A reddish-purple eruption on the upper eyelid

    • accompanied by swelling of the eyelid

    • Most specific rash in DM

    • Only present in a minority of patients.

Generalized erythroderma
Generalized Erythroderma

  • Facial erythema

Flagellate erythema
Flagellate Erythema

  • Erythematous linear streaks on the trunk

  • probably induced by scratching pruritic skin

  • Skin biopsy usually demonstrates an interface dermatitis, typical of other skin lesions in dermatomyositis

Mechanic s hands
“Mechanic’s Hands”

  • roughened, cracked skin at tips and lateral aspects of the fingers resulting in irregular, dirty-appearing lines

Nail changes
Nail Changes

Capillary Loop Dilatation

Nail changes1
Nail Changes

Periungual Erythema


  • Humorally-mediated disorder with cellular infiltrate focused around blood vessels

  • Proinflammatory cytokines contribute to muscle weakness

  • IL-1 and TNF-alpha are increased in muscle tissue

  • Upregulation of MHC class I molecules on myocytes lead to disturbed muscle function


  • Interstitial lung disease

    • 10% of cases

    • respiratory failure may result from diaphragmatic and chest muscle weakness

    • can result in rapid respiratory failure and death

  • Esophageal disease

    • weakness of the striated muscle of the upper 1/3 of the esophagus and/or oropharyngeal muscles

    • can lead to nasal regurgitation, dysphagia, aspiration

    •  More common in elderly patients

    • leads to increased incidence of bacterial pneumonia

  • Myocarditis

  • Malignancy

Outcome predictors
Outcome Predictors

  • Worse outcomes if:

    • delay in initial treatment of >6 months after symptom onset

    • greater weakness at presentation

    • presence of dysphagia

    • respiratory muscle weakness

    • interstitial lung disease

    • associated malignancy

    • cardiac involvement

    • advanced age

Malignancy in dm patients
Malignancy in DM Patients

  • Incidence: of patients with DM, 48%  over age 65 v. 9% under age 65 were found to have a malignancy

  • Risk factors:

    • Evidence of capillary damage on muscle biopsy

    • DM complicated by cutaneous necrosis on the trunk

    • Cutaneousleukocytoclasticvasculitis

    • Older age at diagnosis

  • Pathophysiology: paraneoplastic process

  • Regenerating cells in myositis muscle, but not in normal muscle, express high levels of myositis-specific autoantigens. Same antigens are expressed at high levels in several cancers

  • Types of cancer: adenocarcinoma of the cervix, lung, ovaries, pancreas, bladder and stomach make up about 70% of associated cancers

Cancer screening in dm patients
Cancer Screening in DM Patients

  • Thorough medical history and physical exam

  • Age appropriate cancer screening (mammogram and colonoscopy)

  • CT of chest, abdomen and pelvis recommended only if significantly increased risk

  • Pelvic US and transvaginal US for women

  • Serum CA 125 and CA 19-9

  • PSA

  • UA for blood


  • Improve muscle strength and avoid development of extramuscular complications

  • Glucocorticoids are the cornerstone of initial therapy

  • Typically initiate prednisone at 1 mg/kg to a maximum dose of 80 mg

  • Initial treatment with high doses for the first several months to establish disease control

  • Slow taper to the lowest effective dose for total duration of 9-12 months

  • Assessing treatment response: muscle strength generally a better predictor than serum muscle enzyme concentrations

  • More than 80% of patients will improve with glucocorticoids alone

  • Among those who do respond, the majority do not return to normal strength

Glucocorticoid sparing agents
Glucocorticoid Sparing Agents

  • Starting a sparing agent at the time prednisone is initiated is recommended

  • First line agents include azothioprine or methotrexate

  • Azothioprine is preferred if patients have ILD, underlying liver disease, or are unwilling to abstain from alcohol

    • A randomized trial compared prednisone + azothioprine to pred alone; no difference in clinical outcomes at 3 months, but at 3 years combination group required less maintenance prednisone

    • Response to azothioprine may take as long as 4-6 months

  • Before beginning azothoprine, patients should be screened for thiopurinemethytransferase deficiency (TPMT); if heterogeneous for this allele, pts can tolerate azothioprine but require lower daily doses

  • Homozygous negative pts, occuring in 1:300 people, cannot metabolize the drug and should not receive under any circumstances  can lead to disasterous BM toxicity

  • Initial dose of azothioprine is 50 mg/day