Skip to Main Content

++

DERMATOMYOSITIS/JUVENILE DERMATOMYOSITIS (JDM)

++

DEFINITION

++

Most common pediatric inflammatory myopathy.

++

Bohan and Peter diagnostic criteria (definite JDM: heliotrope rash or Gottron’s papules plus at least three criteria; probable JDM: heliotrope rash or Gottron’s papules plus two criteria)

++

  • Heliotrope rash (eyelids) or Gottron’s papules (extensor surfaces)

  • Progressive symmetric proximal muscle weakness

  • Elevated skeletal muscle enzymes (CK, AST, aldolase, LDH)

  • EMG consistent with myopathy

  • Biopsy evidence of myositis

  • Updated criteria will likely include muscle abnormalities on MRI STIR or T2 sequence

++

EPIDEMIOLOGY

++

  • Incidence: About 2–3 cases/million children

  • Peaks at 6 years and 11–12 years of age; female:male is 2:1

  • Comparable for blacks and whites, lower in Hispanics

  • Unlike in adults, JDM has no definite associations with malignancy

++

ETIOLOGY

++

  • Potential infectious triggers: Group A beta-hemolytic Streptococcus, coxsackie virus B, parvovirus, others

  • HLA and TNF-α alleles may predispose a child to JDM

  • Molecular mimicry is suspected

  • Sun exposure may trigger onset of rash

++

DIFFERENTIAL DIAGNOSIS

++

  • Rheumatologic:

    • ✓ Juvenile polymyositis is rare in children (2–8% of inflammatory myopathies), has similar age and sex distribution as JDM but includes proximal and distal weakness, muscle atrophy, lacks skin abnormalities, and calcinosis is rare

    • ✓ Systemic lupus erythematosus (SLE) and related conditions (e.g., mixed connective tissue disease, Sjögren syndrome)

    • ✓ Scleroderma

    • ✓ Juvenile idiopathic arthritis (JIA); polyarticular or systemic

    • ✓ Polyarteritis nodosa

    • ✓ Eosinophilic fasciitis

  • Infectious:

    • Viral myopathies: Influenza A and B, coxsackie, Epstein–Barr virus, herpes, parainfluenza, adenovirus, enterovirus

    • Bacterial and parasitic myopathies: Staph, strep, toxoplasma

  • Metabolic/Genetic:

    • ✓ Muscular dystrophies

    • ✓ Congenital myopathies

    • ✓ Myotonic disorders

    • ✓ Glycogen storage diseases

    • ✓ Periodic paralysis

    • ✓ Endocrinopathies

  • Other:

    • ✓ Trauma

    • ✓ Toxins

    • ✓ Drug-induced myopathies

    • ✓ Disorders of neuromuscular transmission

++

PATHOPHYSIOLOGY

++

  • Perivascular inflammation, mostly mononuclear cells

  • Swelling and blockage of capillaries, tissue infarction, perifasicular atrophy

  • Chronic inflammation ensues with fibrosis and microscopic calcification

++

CLINICAL MANIFESTATIONS

++

  • Proximal muscle weakness (neck flexors, shoulders, abdomen, thighs): Gower sign, difficulty climbing stairs or combing hair

  • Skin: Heliotrope rash (violaceous rash of eyelids); facial erythema, possibly in malar distribution; papulosquamous eruption on extensor surfaces (Gottron’s rash), particularly over interphalangeal joints (Gottron’s papules); shawl sign (erythematous rash in a shawl distribution); cutaneous calcinosis and ulceration

  • Nailfolds: Capillary drop-out, capillary dilation, cuticular hypertrophy

  • Arthritis: Effusions, limited range of motion, pain, deformity

  • Mucocutaneous: Oral ulcers, gingival inflammation

  • Pulmonary: Shortness of breath, cough, crackles can be consistent with interstitial lung disease or aspiration pneumonia

  • Gastrointestinal: Dysphagia, ulceration, perforation, bleeding, constipation, diarrhea, abdominal pain

  • Other manifestations: Lipodystrophy, polyneuropathies, retinal exudates, and cotton wool patches

  • Other complications: Calcinotic lesions may spontaneously drain causing local inflammatory response and superinfection; can form exoskeleton; vasculitic ulcers; rare arrhythmias and cardiomyopathy; complications of chronic corticosteroid exposure (growth failure, hypertension, vertebral compression fractures, striae, avascular necrosis, cataracts, glaucoma)

++

DIAGNOSTICS

...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.