Dermatomyositis

• Wagner 1863
• Unverricht 1887

Polymyositis

Rare antibody- or immune complex-mediated autoimmune disease, which belongs to the group of inflammatory myopathies.

• Incidence (children): 2-7/1'000'000/year
• Incidence (adults): 6-10/1'000'000/year
• Peak of incidence (adults): ca. 40 LY and v. 55-60 yrs
• Peak in incidence (children): 5-14 yrs
• African-Americans > Caucasians
• Women : men = up to 2 : 1

• Clinical are distinguished (with frequencies):
  • Type I: adult polymyositis
  • Type II: typical adult dermatomyositis with skin/muscle involvement
  • Type III: typical adult dermatomyositis with malignant tumours
  • Type IV: Typical dermatomyositis of the adult of childhood (especially after infection of the respiratory tract)
  • Type V: Polymyositis with myoglobulinuria (acute myolysis)
  • Type VI: Polymyositis with Sjörgren's syndrome
  • Type VII: Polymyositis with other collagenoses

• UV light may lead to exacerbation of dermatomyositis
• Genetic predispositions:
  • Idiopathic myositis: HLA-B8, HLA DRB 03
  • Classic and juvenile dermatomyositis: HLA-A68, HLA-DR3
  • Drug-associated dermatomyositis: HLA-B 08, HLA-DR4 haplotypes
  • Amyopahtic dermatomyositis: no HLA associations
• Infections:
  • Picornaviruses
  • Coxsackieviruses
  • AIDS
  • HTLV-1
• Medications:
  • D-penicillamine
  • Procainamide
  • NSAR
  • Simvastatin
  • Antimalarials
  • Interferon α
  • Allopurinol
• Neoplasia

• General symptoms
• Fatigue
• Myalgias (muscle-cartilage-like)
• Problems combing hair and other daily activities

• Cutaneous symptoms:
  • Facial swelling with eyelid oedema
  • Pruriginous or mildly dolente, lilac erythema on the face and décolleté
  • "Weepy facial expression"
  • Heliotropic erythema of the eyelids
  • Cheeks: butterfly-shaped erythema
  • Shawl sign: perioral recess erythema
  • Atrophic, hypo- or hyperpigmentation
  • Gottron's sign
    • In 70% of patients
    • pathognomic
    • Striated erythema and papules on the finger extensor sides
  • Nailfold hyperkeratoses with telangiectasia and telangiectasia
    • Keining's sign = pain when trying to push back the nail fold
  • Rhagades of the fingertips
  • Scleroderma-like indurations
  • Raynaud's syndrome
  • Uncharacteristic psoriasiform, lichen planus-like exanthema
  • Diffuse effluvium
  • Poikiloderma
• Musculature:
  • Muscle weakness, especially proximal limb sections (neck, shoulder girdle, legs)
  • Symmetric muscle weakness/ myalgias/ muscle atrophies/ contractures
  • Pharyngeal and laryngeal muscles may also be affected
  • Calcifications of the musculature are possible
  • Dermatomyositis sine myositis or amyopathic dermatomyositis are called dermatomyositides without muscle involvement

• Bones and joints:
  • Osteoporosis
  • Arthralgias
  • Arthritides
  • Symmetric polyarthritis, also known as oligo- or monarthritis

• Overlap syndromes are possible

• Other (rare) organ involvement of
  • Heart
  • Intestine
  • Kidneys

• Lab
  • All laboratory values listed may be normal despite the presence of dermatomyositis.
  • BSG ↑, CRP ↑.
  • Blood count: leukocytosis, lymphopenia, eosinophilia.
  • ↑ Serum creatinine phosphokinase, aldolase, CPK, GOT, GPT, LDH
  • Antinuclear antibody (ANA) positive in approx. 1/3 of cases.
  • Jo-1 in 20%
  • PM-Scl 5%
  • nRNP 5%
  • Anti-Mi 10-30%
  • PL-7 < 3%
  • PL-12 < 3%
  • OJ in < 3%
  • EJ in < 3%
  • Serum electrophoresis: α2- and γ-globulin.
  • Urine: creatinine and creatinineuria. Proteinuria in relapse, myoglobinuria.

• Clinic
• Laboratory:
  • blood sedimentation rate, C-reactive protein, liver and kidney values, creatinine kinase, aldolase, LDH, rheumatoid factor
  • Thyroid antibodies
  • ANAs and ENAs
• U status/creatin excretion in 24-hour urine
• Biopsy:
  • Skin biopsy
  • Muscle biopsy
• Electromyogram: polyphasic potentials
• Capillaroscopy
• Tumour exclusion

• To diagnose "polymyositis", at least 3 of the following criteria should be positive:
  • Muscle enzymes (creatinine kinase)
  • Electromyogram: polyphasic potentials
  • Muscle biopsy

• Unpredictable
• 5-year survival rate at 95% or the 10-year survival rate at 84%

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