Dermatomyositis

DERMATOMYOSITIS

  • Dermatomyositis is an idiopathic inflammatory myopathy with proximal weakness and characteristic cutaneous findings.
  • It has biphasic peaks. Seen in children aged 7-15 years and adults aged 30-50 years.
  • It is more predominant in females.

PATHOPHYSIOLOGY

  • Dermatomyositis is mediated by Type 1 interferon cytokine family (IFN alpha, IFN beta)
  • Classic antibodies associated are anti-Mi-2 against helicase and anti-Jo-1 (antisynthetase antibody).
  • Muscle pathology involves injury to muscle capillaries and perifascicular atrophy (injury to muscle fibers at the end of muscle fascicles).
  • Skin pathology involves injury to the basal layer of keratinocytes.

SIGNS AND SYMPTOMS:

Skin
  • Gottron’s sign/papules: Violaceous lesions that can be flat (Gottron sign) or raised (Gottron papules) over dorsal metacarpophalangeal and interphalangeal joints of the hands, elbows, knees.
  • Heliotrope rash: Violaceous periorbital macular erythema with or without edema.
  • Butterfly-shaped, malar erythematous rash (note that malar refers to its site: the cheek and butterfly refers to its shape).
    • It crosses the nasolabial folds because this distinguishes it from the malar rash of systemic lupus erythematosus, which spares the nasolabial folds.
  • Erythema and poikiloderma on the photo exposed areas –
    • On the Chest (V SIGN)
    • On the Shoulder, Neck, Back (THE SHAWL SIGN)
  • Calcinosis cutis, which is aberrant calcium depositions in the skin and subcutaneous tissues, which cause yellowish or white dermal lesions and stiffening with finger joint immobility.

Muscle
  • Symmetric proximal muscle weakness (muscle weakness when combing hair, reaching for objects overhead, rising from a seated position, climbing stairs).
  • Extensor muscles are more often affected than the flexor muscles.
Systemic Manifestations
  • Dysphagia, GERD
  • Myocarditis
  • Interstitial lung disease
  • Dysphonia
  • Subcutaneous calcifications (Calcinosis cutis)
  • Flexion contracture of the ankles (tip toe gait in children)
  • Malignancies are common in adults, maybe related to cross reacting autoantigens in the muscle and on tumor cells: Most common malignancies are adenocarcinoma (Ovarian, lung, stomach, pancreatic, colorectal).

DIAGNOSTIC CRITERIA

  1. Diagnostic skin involvement (Gottron’s papule, Heliotrope rash) or diagnostic muscle biopsy findings (Perifascicular atrophy)

OR,

  1. All of the following –
  • Suggestive skin involvement
  • Subacute or chronic proximal or distal weakness
  • Muscle biopsy showing perimysial or perivascular inflammation without features suggesting another disorder OR skin biopsy showing interface dermatitis along with clinical exclusion of SLE.

LABS:

  • Elevated Creatine phosphokinase(CPK) generally 10 times the upper limit or normal but can vary (↑↑CPK)
  • Abnormal Aldolase and LDH (↑Aldolase and ↑LDH)
  • Antibody studies(anti-Mi 2, anti-Jo-1, anti-MDA5)
  • ↑ALT & ↑AST

IMAGING:

  • MRI, EMG

BIOPSY:

  • Skin biopsy (interface dermatitis)
  • Muscle biopsy (Perifascicular atrophy, Perivascular and Perimysial inflammation)

 

 

MANAGEMENT

Pharmacological
  • Corticosteroids are the first line( typically Prednisolone 1mg/kg/day orally until significant improvement occurs and then gradual taper).
  • Second line are Methotrexate, azathioprine, cyclosporine, IVIG.
Non pharmacological
  • Avoid sun exposure
  • Physical therapy.

Ref: Goldman-Cecil Medicine, Medscape, Uworld, Drawittoknowit, Amboss

5 2 votes
Article Rating
Recommended Posts
Septoplasty

Septoplasty or alternatively submucous septal resection and septal reconstruction, is

Scabies

SCABIES Human scabies is caused by an infestation of the

Subscribe
Notify of
guest
0 Comments
Inline Feedbacks
View all comments