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  1. Diagnostic Criteria: (4 out of 5, for dermatomyositis cutaneous changes must present)
    1. Proximal symmetric progressive muscle weakness
    2. Elevated muscle enzyme
    3. Consistent electromyography (EMG)
    4. Consistent muscle biopsy
    5. Cutaneous disease
  2. Classification
    1. Primary dermatomyositis
    2. Primary polyomyositis
    3. Associated with underlying malignancy
    4. Overlaps syndrome
    5. Childhood dermatomyositis
    6. Amyopathic dermatomyositis
For this purpose, the hallmark cutaneous manifestations of DM are presumed to be present if the following conditions are met: presence of two major criteria or one major criterion and two minor criteria or one major criterion and two minor criteria (biopsy of at least one skin lesion should show changes consistent with cutaneous DM).
  1. Major Cutaneous Criteria
    1. Heliotrope rash
      Macular violaceous erythema with our without associated scale of the eyelids or periorbital skin. Secondary or associated cutaneous findings, such as scale, pigmentary change, telangiectasia, or edema also can be present.
    2. Gottron’s papules
      Violaceous papules or small plaques overlying the dorsal or dorsal-lateral aspects of interphalangeal or metacarpophalangeal joints. When fully formed, these papules become slightly depressed at the center, which can assume a white, lacy appearance. Associated scale-hyperkeratosis, pigmentary change, or telangiectasia may be present.
    3. Gottron’s sign
      Macular violaceous erythema with or without associated scale-hyperkeratosis, pigmentary change, or telangiectasia involving extensor aspects of the knuckles, elbows, knees, or medial malleoli.

Gottron’s papule

Gottron’s sign

Heliotrope rash

V sign

  1. Minor Cutaneous Criteria
    1. V-area of neck or upper chest (open collar area; V-sign)
    2. Nape of die neck or posterior aspect of shoulders (shawl sign)
    3. Lateral surface of thighs or hips (holster sign)
  2. Mechanic’s Hand Lesions
    1. Cutaneous calcinosis
    2. Cutaneous ulcers
    3. Pruritus
Cutaneous signs of dermatomyositis 
1. Gottron's papules: - lilac or violaceous papules on knuckle, dorsa of hands. 
2. Gottron's sign: - Violaceous erythema with edema over shoulder, arms, forearms. 
3. Heliotrope sign: - Violaceous erythema with edema over eyelids, periorbital region. 
4. Poikiloderma: - Atrophy of skin, hypopigmentation, dilated blood vessels over trunk. 
5. Mechanic hand: - Symmetric hyperkeratosis along ulnar aspect of thumb and radial aspect of fingers. 
6. Shawl Sign: - Violaceous erythema extending from dorsolateral aspect of hands, forearms, and arms to shoulder & neck. 
7. Calcinosis cutis: - Calcium deposits in skin (in Juvenile variant). 
8. Miscellaneous signs: - Photosensitivity, vasculitis, panniculitis, Nail-fold telangiectasia.
  1. Other Findings
    Proxmial muscle weakness and tenderness, dysphagia, cardiac and pulmonary disease.
    This is characterized by skin rash, muscle weakness and tenderness. In addition to skin and skeletal muscle involvement, there may be involvement of muscles of gastrointestinal system (dysphagia and aspiration), heart (cardiomyopathy, arrhythmias), and lung (pulmonary fibrosis).
  2. Epidemiology
    Dermatomyositis (DM) is an uncommon condition. Female is twice as commonly affected as male. In young female patients it is associated with autoimmune connective tissue diseases. There may be underlying systemic malignancy, particularly for patients over 40 years old. DM is more often associated with malignancy than polymyositis. Common malignancies include breast, lung, gastrointestinal, ovarian cancer, and in our locality nasopharyngeal carcinoma in males and ovarian carcinoma in females. The cancer may precede, occur simultaneously, or follow DM. Removal of underlying malignancy may be associated with resolution of DM, and recurrence of malignancy may lead to relapse of DM.

    Clinical Features
    1. Presentation and clinical course may be: acute, subacute, chronic.
    2. The severity of cutaneous involvement does not correlate particularly well with severity of associated myositis. Muscle involvement without cutaneous features is termed polymyositis. Cutaneous involvement may precede muscle involvement, or occur without apparent muscle involvement.
  3. Muscle Involvement Include:
    1. Muscle pain and tenderness affecting trunk, limb girdles and proximal limbs.
    2. Muscle weakness is symmetrical and bilateral.
    3. Weakness is progressive, with difficulty rising from low chairs, climbing stairs, and holding arms above shoulder during combing hair.
    4. Facial and bulbar muscles are usually spared, but may be affected in cases associated with m alignancy or myasthenia. Dysphagia may occur due to oesophageal involvement, arrhythmia and cardiac failure due to myocarditis.
  4. Cutaneous Features Include:
    1. Violaceus erythema and oedema of periorbital region, especially upper eyelids. There may be diffuse redness and swelling of entire face, extending to other sun-exposed areas. Heliotrope rash
    2. Photosensitivity, poikiloderma (erythema, pigmentation, telangiectasia, atrophy) of face and upper chest shoulders and arms.
    3. Red to violaceous patches and plaques over extensor surface of elbows and knees.
    4. Gottron's sign refers to such patches and plaques over knuckles (dorsal surfaces of interphalangeal joints). In LE, similar changes are characteristically located on dorsal phalanges between the phalangeal joints instead.
    5. Raynauds phenomenon, periungal erythema and telangiectasia.
    6. Lupus like and sclerodermatous skin involvement.
    7. Calcinosis, chronic ulcers. Calcinosis universalis in juvenile DM.
  5. Childhood Form Of Dm Is Often Slow And Progressive, Characterized By Calcinosis. The calcinosis often involve intermuscular fascial planes, but may be subcutaneous and acral (elbow, knees, fingers) as in adults.
    Juvenile DM are usually steroid responsive, but often associated with contractures and deformity, leading to functional disability and morbidity. One variant is characterized by vasculitis of muscles and gastrointestinal tract, rapid onset of severe weakness, steroid unresponsiveness and death. Internal malignancy is seldom seen in either type.
  6. Diagnosis Is Essentially Clinical, as cutaneous histopathological features are non-specific.
    1. There is vacuolar interface dermatitis with sparse superficial perivascular lympho-histiocytic infiltrate, which is consistent but not diagnostic of DM. Immuno-fluorescence studies do not show significant immune deposits at dermo-epidermal junction.
    2. Skin biopsy may differentiate LE from DM when clinical features are nonspecific, but this is also difficult unless characteristic LE histopathological features are present
  7. Assess Extent of Involvement
    1. Muscle enzymes CPK, AST, LDH are performed to document myositis and assess progress during treatment. Muscle enzymes are not specific of DM, it may be elevated in other situations or apparently normal in DM without significant muscle involvement. Twenty four hour urine for creatine may increase sensitivity, but is not readily available.
    2. Muscle involvement is often focal, and electromyography EMG may help to locate the affected muscles. Random muscle biopsy is subjected to sampling errors. Magnetic resonance imaging (MRI) has recently been investigated as a sensitive tool for locating subclinical myositis and guide muscle biopsy, even if muscle enzymes and EMG were apparently normal.
    3. ECG and echocardiography may be necessary as clinically indicated to assess cardiac involvement. Lung function may be need to monitor respiratory muscle involvement. Barium swallow to assess pharyngeal and eosophageal motility, and aspiration.
  8. Auto-Immune Screen
    These investigations may help to differentiate DM from other auto-immune connective tissue diseases and overlapping syndromes, in conjunction with clinical features.
    1. ANA is present in both LE and DM.
    2. Anti-double stranded DNA, low C3 and C4 (systemic LE).
    3. Anti-ENA, Anti-U1RNP (Mixed Connective Tissue Disease).
    4. Anti-Ro, Anti-La (Subacute cutaneous lupus and Sjogrens syndrome).
    5. Anti PM-Scl (Polymyositis scleroderma overlap syndrome).
    6. Anti-Jo1 (histidyl tRNA synthetase) antibody, polymyositis with interstitial lung disease, pulmonary fibrosis.
  9. Treatment
    1. Treatment of skin diseases:
      1. Sun-protection: Topical steroids
      2. Antimalarials: Hydroxychloroquine (below 6.5 mg/kg/day), same as for cutaneous LE.
      3. Systemic steroids are sometimes used but generally more effective in controlling myositis than cutaneous manifestations Systemic steroids may cause steroid myopathy with prolonged use, leading to paradoxical decrease in muscle weakness following steroid dosage reduction.
    2. Treatment of Muscle Involvement:
      This should preferably be managed in conjunction with physicians.
      1. Bed rest during the acute phase. Physical therapy, physiotherapy especially important in juvenile DM to prevent contractures and deformity.
      2. Systemic steroids are the mainstay of therapy for myositis. Initial dose of prednisolone is 1 mg/kg/day, with dose adjusted according to clinical response and muscle enzymes.
      3. Methotrexate, azathioprine, cyclophosphamide, cyclosporin as immunosuppressives and steroid sparing agents.
      4. Pulse intravenous methyl-prednisolone, plasmapheresis and intravenous immunoglobulin infusion have been tried in acute life threatening stages for rapid control and stabilization.
  10. Scleroderma
    1. Scleroderma describes the thickening and hardening of the skin due to progressive accumulation of dermal collagen, leading to fibrosis and loss of mobility of skin.
    2. It can exist as cutaneous or systemic form. Cutaneous forms are morphea, linear scleroderma, and generalised morphea, these are confined to the skin as tight indurated plaques.
    3. Systemic sclerosis refers to a similar process involving not only the skin but internal organs as well, and may lead to organ failure or even death.
    4. Organs affected include lung, gut, kidneys, heart and skeletal muscle.
    5. Common causes of death are aspiration pneumonia, pulmonary fibrosis, and renal failure

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