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autoimmune disease targeting muscles and skin in genetically predisposed individuals

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  1. 1. Dermatomyositis Habakuk larry omondi
  2. 2. Definition • Chronic immune-mediated disorder • Affects the skin and/or proximal skeletal muscles • Idiopathic inflammatory myopathy with characteristic cutaneous lesions with or without muscle inflammation and weakness
  3. 3. Classification 1. Adult dermatomyositis: • Classic DM • Classic DM with malignancy • Classic DM with associated connective tissue • disease • Clinically amyopathic DM (CADM) 2. Juvenile DM (JDM) • Classic JDM • Clinically amyopathic JDM
  4. 4. Epidemiology • Rare. • Incidence 9.63 cases per million population. • Adult 50yrs • children 5-10 yrs • More common in women • The diagnosis of cutaneous dermatomyositis is often missed or delayed, because the pruritus and rash associated with it are very similar to other forms of dermatitis • Increased risk of malignancy
  5. 5. Etiology • Cause is not Known • Both genetic and environmental factors play a role in its pathogenesis. • Associated with HLADR3,DR5,DR7 • Statins, hydroxyurea and penicillamine have also been associated with DM
  6. 6. pathophysiology • Due to humoral attack to muscle capillaries and small arterioles(endothelium of the endomysial blood vessels). • MAC, B cells and CD4 deposited on endomysial vasculature destroy capillaries. • Muscles undergo microinfarction
  7. 7. Clinical presentation Cutaneous Findings • Occur 2 to 3 months prior to muscle weakness Primary lesion: pruritic erythematous violaceous patches and plaques with or without scale. • Poikiloderma may be present. • Lesions frequently involve scalp, anterior/posterior neck, photoexposed areas and extremities, but can involve any body area
  8. 8. • Heliotrope rash: first cutaneous sign: periorbital, symmetric, violaceous patches with or without edema • Gottron’s papules: violaceous papules overlying the following joints of the dorsal hands: metacarpophalangeal, distal interphalangeal, and/or proximal interphalangeal • Gottron’s sign: violaceous symmetric macular erythema over bony prominences of hands and elsewhere (e.g., elbows, knees, medial malleoli)
  9. 9. • Tendon streaking: linear violaceous erythema along extensor tendons of hands/feet • Nailfold capillary changes: correlated with disease severity; capillary telangiectasia, infarcts, capillary loop dropout • V- sign: macular erythema and poikiloderma of V- area of neck and chest • Shawl sign: macular erythema and poikiloderma of upper back and shoulders
  10. 10. • Holster sign: erythematous patches/plaques on bilateral hips • Malar rash: erythema of the central face but unlike ACLE, usually does not spare nasolabial folds • Mechanics hands: hyperkeratosis of the palmar and lateral surfaces of the fingers, associated with interstitial lung disease • Calcinosis cutis: cutaneous calcium deposition, usually in areas of trauma,
  11. 11. Extracutaneous findings • Proximal symmetric muscle weakness (shoulder and limb girdle) • Dysphagia/dysphonia (esophageal/pharyngeal involvement) • Pulmonary disease: Restrictive lung disease from respiratory muscle weakness and Interstitial lung disease which is the leading cause of mortality • Synovitis • Raynaud’s phenomenon • Cardiac disease: rare ECG changes,
  12. 12. Heliotrope (reddish purple) erythema of upper eyelids and edema of the lower lids
  13. 13. Gottron papules and nailfold telangiectasia
  14. 14. Dermatomyositis is often associated with a poikiloderma in a photodistribution
  15. 15. Diffuse alopecia with scaly scalp
  16. 16. • Diagnostic criteria: (3 criteria plus the rash) • Symmetrical muscle weakness: limb girdle muscles and anterior neck flexors • Muscle biopsy: evidence of muscle fiber necrosis, inflammatory exudate, often perivascular • Elevated muscle enzymes: CPK, aldolase, LDH • EMG triad: small polyphasic action potentials, positive sharp waves and insertional irritability and bizarre high frequency repetitive discharges • Cutaneous changes: heliotrope rash with periorbital edema; scaly dermatitis
  17. 17. Diagnosis Lab tests • During acute active phase: elevation of creatine phosphokinase (65%), most specific ; aldolase(40%) • Autoantibodies to 155 kDa and/or Se in 80% and to Jo-1 in 20% (both have a high specificity for DM) and to (low specificity) antinuclear antibodies (ANA) in 40%. • Urine-elevated 24-h creatine excretion (>200 mg/24 h).
  18. 18. • Pulmonary function studies with diffusion capacity • ECG • Esophageal manometry • Colonoscopy • PAP smear • Imaging studies;MRI or U/S of muscles, chest x-ray,barium swallow, electromyography, CT
  19. 19. • Muscle biopsy-perivascular and interfascicular inflammatory infiltrates with adjoining groups of muscle fiber degeneration/regeneration.
  20. 20. Management Prednisone • 0.5 to 1 mg/kg body weight per day, increasing to 1.5 mg/kg if lower dose ineffective. Taper when "muscle enzyme" levels approach normal. • Best if combined with azathioprine, 2 to 3 mg/kg per day.
  21. 21. Management cont. • Sun avoidance • Sunscreens and photoprotective clothing • Topical corticosteriods • Antimalarial agents(hydroxychloroquine, chloroquine) • MTX • Mycophenolate mofetil • Immune globulins
  22. 22. • Surgical excision of focal, tender calcinotic lesions