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Dermatomyositis

Muscles Symmetric proximal extremity muscle weakness (extensors) - Check for bibasilar fine crackles/rales - 15-30% develop interstitial lung disease - Poor prognosis

- Optional - Electromyography: If muscle enzymes (-) - Muscle biopsy: Gold standard; consider if above negative - MRI: If above negative or to help localize place to biopsy - Skin biopsy: Lupus will have similar features

- Screen for other organ involvement - Pulmonary function tests with diffusing capacity - Baseline EKG - Esophageal study (except if amyopathic)

- Malignancy work-up in women - Pelvic, breast, rectal exam - CBC, CMP, urinalysis, TSH, stool occult blood test, colonoscopy (if age appropriate), PAP smear, CA-125 - CT chest/abdomen/pelvis - Transvaginal pelvic ultrasound

- First line - Oral prednisone: 1-2 mg/kg/day tapered to 50% over 6 months, and to zero over 2-3 years (1)[A]; especially if swallowing problem - Option to use pulse, split dose, or alternate day (1)[B]

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  • Check for bibasilar fine crackles/rales15-30% develop interstitial lung diseasePoor prognosis
  • Risk aspiration pneumonia and respiratory failure due to respiratory muscle weakness
  • Conduction defects, myocarditis, congestive heart failure
  • May be under-recognized; major prognostic factor for death
  • Nonerosive arthritis of small joints

Tests

Lab

  • Muscle enzymes: Creatine kinase (CK), aldolase may be elevatedEarly disease or amyopathic disease may have no elevation.CK most sensitive. Others affected: Lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase
  • Autoantibodies: Help define subtypes but role in pathogenesis unclear. Not useful for diagnostic purposes but helpful for prognosisAntinuclear (ANA) (+1/3 patients)Anti-Jo-1 (anti-histidyl-tRNA synthetase) (+ in 20%)70% increased risk for interstitial lung disease; associated with anti-synthetase syndromeAnti-Mi-2 (anti-nuclear helicase) (+ in 5-15%)

Surgery

  • OptionalElectromyography: If muscle enzymes (-)Muscle biopsy: Gold standard; consider if above negativeMRI: If above negative or to help localize place to biopsySkin biopsy: Lupus will have similar features
  • Screen for other organ involvementPulmonary function tests with diffusing capacityBaseline EKGEsophageal study (except if amyopathic)
  • Malignancy work-up in womenPelvic, breast, rectal examCBC, CMP, urinalysis, TSH, stool occult blood test, colonoscopy (if age appropriate), PAP smear, CA-125CT chest/abdomen/pelvisTransvaginal pelvic ultrasound

Differential Diagnosis

  • Cutaneous findings:Systemic lupus erythematosus, psoriasis, airborne or contact dermatitis, photodrug eruption, cutaneous T-cell lymphoma, atopic dermatitis, scleroderma
  • Muscle findings and elevated creatine phosphokinase:Polymyositis, hypothyroidism, viral myositis, rhabdomyolysis, trichinosis, myasthenia gravis

Treatment

  • There is a discordance between response of muscle disease and that of dermatologic disease to systemic therapy.
  • Treatment depends on presence of muscle disease and organ involvement.
  • Only FDA-approved drug is intravenous immunoglobulin (IVIG); however, other medications are considered first line.

Cutaneous Disease

  • First lineSunscreen (broad-spectrum UVB/UVA) (1)[C]High-potency topical steroid (including face) — 2 weeks then switch to topical calcineurin inhibitor (Protopic ®, Elidel ®) (1)[C]Treat pruritus (hydroxyzine, diphenhydramine) (1)[C]
  • Second line (if severe)Hydroxychloroquine (1)[B]

20% with dermatomyositis develop morbilliform eruption with hydroxychloroquine

  • Hydroxychloroquine plus quinacrine (1)[C]
  • Methotrexate: Low-dose weekly (1)[B]
  • Mycophenolate mofetil (CellCept ®)(1)[B]
  • IVIG (1)[A]
  • Thalidomide (1)[C]
  • Dapsone (1)[C]

Muscle Disease

  • First lineOral prednisone: 1-2 mg/kg/day tapered to 50% over 6 months, and to zero over 2-3 years (1)[A]; especially if swallowing problemOption to use pulse, split dose, or alternate day (1)[B]Often with addition of steroid sparing agent:Methotrexate: Low-dose weekly (1)[B]Mycophenolate mofetil (CellCept ®) 2.5 g/day divided (1)[B]Azathioprine: 2-3 mg/kg/day (1)[C]
  • Second line +/- prednisoneAzathioprine"‚+ methotrexate (1)[B]IVIG (1)[A]; can combine with any of aboveCyclosporine (1)[B]
  • Third lineRituximab (1)[C]TNF-alpha inhibitors (1)[B]

TNF blockers can also induce dermatomyositis.

  • First line
  • Second line +/- prednisoneCyclophosphamide (2)[A]Azathioprine (2)[C]Methotrexate (2)[C]

Additional Treatment

General Measures

  • Physical therapy to prevent contractures, avoid aggressive weight training.
  • If severe muscle inflammation, bed rest can be of benefit.
  • If dysphagia, elevation of head of bed and avoid eating before bed.

Issues for Referral

Multidisciplinary care: Rheumatology, dermatology, neurology, oncology (if cancer-associated), pulmonary

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

  • Monitor regularly for esophagus, lung, cardiac, joint involvement
  • If amyopathic, monitor CK closely; muscle strength exams at 1-3 month intervalsIf no muscle involvement at 2 years, can consider "amyopathic,"ť but with continued muscle strength screeningIf muscle disease confirmed, systemic therapy needed
  • Malignancy screening yearlyHighest risk in first 2-5 years, but risk does not return to zero

Patient Education

Aggressive sun protection: Sun-protective clothing; broad-spectrum UVB/UVA sunscreen

Prognosis

  • Long-term outcomes are variable and range from remission to progressive disease to death.20% may spontaneously remit, 5% may have a fulminant, progressive course.Death occurs in about 10-20%, with worse prognosis if cancer-associated, pulmonary or cardiac involvement, or elderly.
  • Skin disease presents first in 50% of patients. Myositis typically follows 3-6 months later.

Complications

  • Treatment-related: Infections and medication side effects
  • Muscle-related difficulty swallowing or chest muscle weakness: Weight loss and malnutrition; aspiration pneumonia; respiratory failure
  • Skin: Calcium deposits; skin breakdown; Raynaud's syndrome

References

1Iorizzo LJ 3rd, Jorizzo JL. The treatment and prognosis of dermatomyositis: An updated review. J Am Acad Dermatol. 2008;59(1):99-112. [View Abstract]2Connors G, Christopher-Stine L, Oddis CV. Interstitial lung disease associated with the idiopathic inflammatory myopathies: What progress has been made in the past 35 years? Chest. 2010;138(6):1464-1474. [View Abstract]

Additional Reading

1Goreshi R, Chock M, Foering K. Quality of life in dermatomyositis. J Am Acad Dermatol. 2011;65(6):1107-1116. [View Abstract]2Madan V, Chinoy H, Griffiths CE. Defining cancer risk in dermatomyositis. Part I. Clin Exp Dermatol. 2009;34(4):451-455. [View Abstract]

Codes

ICD9

710.3 Dermatomyositis

ICD10

  • M33.10 Other dermatopolymyositis, organ involvement unspecified
  • M33.90 Dermatopolymyositis, unsp, organ involvement unspecified
  • M33.91 Dermatopolymyositis, unsp with respiratory involvement
  • M33.99 Dermatopolymyositis, unsp with other organ involvement

SNOMED

  • 396230008 dermatomyositis (disorder)
  • 238935002 dermatomyositis sine myositis (disorder)
  • 46696008 dilated cardiomyopathy secondary to dermatomyositis (disorder)

Clinical Pearls

  • Amyopathic dermatomyositis (DM), in addition to classic DM, can be associated with both pulmonary disease and malignancy.
  • Risk of malignancy highest in first 2-5 years, but risk does not return to zero.
  • Pulmonary involvement is not universal, but is an important cause of morbidity and mortality.
  • The mainstay of therapy for classic dermatomyositis (skin and muscle involvement) is long-term systemic steroids, often in conjunction with a steroid-sparing systemic agent.
  • Myopathy usually resolves with therapy. However, skin is often resistant.
  • Quality of life significantly reduced.