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Muscles Symmetric proximal extremity muscle weakness (extensors)
- Check for bibasilar fine crackles/rales
- 15-30% develop interstitial lung disease
- Poor 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 elevated
- Early 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 prognosis
- Antinuclear (ANA) (+1/3 patients)
- Anti-Jo-1 (anti-histidyl-tRNA synthetase) (+ in 20%)
- 70% increased risk for interstitial lung disease; associated with anti-synthetase syndrome
- Anti-Mi-2 (anti-nuclear helicase) (+ in 5-15%)
Surgery
- 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
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 line
- Sunscreen (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 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]
- 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 +/- prednisone
- Azathioprine"‚+ methotrexate (1)[B]
- IVIG (1)[A]; can combine with any of above
- Cyclosporine (1)[B]
- Third line
- Rituximab (1)[C]
- TNF-alpha inhibitors (1)[B]
TNF blockers can also induce dermatomyositis.
- First line
- Second line +/- prednisone
- Cyclophosphamide (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 intervals
- If no muscle involvement at 2 years, can consider "amyopathic,"ť but with continued muscle strength screening
- If muscle disease confirmed, systemic therapy needed
- Malignancy screening yearly
- Highest 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.