Dermatomyositis

INTRODUCTION:
  • A systemic connective tissue disease characterized by inflammatory and degenerative changes in the muscles (polymyositis) and frequently also in the skin (dermatomyositis), leading to symmetric weakness and some degree of muscle atrophy, principally of the limb girdles.
SYMPTOMS & SIGNS
  • Dermato + Myositis: Involves Skin and muscles usually.
  • Females are more commonly affected. Features are 'rash and muscle weakness'.
  • 'Proximal' muscle weakness with loss of fine motor movements is seen.
  • Dermatomyositis can be associated with malignancy in 10-20% cases.
  • Rash involves
  1. Eyelids with edema (Heliotrope rash) 
  2. Erythema of knuckles with scaly eruption (Gottron rash)
  3. Neck and anterior chest (V sign)
  4. Back and shoulder (Shawl sign)
  • Creatine kinase is increased especially in damage to muscles and in conditions like:
  1. Myocardial infarction
  2. Trauma to muscles (Rhabdomyolysis)
  3. Muscular dystrophies
  4. Dermatomyositis 
  5. Polymyositis
  6. Hypothyroidism and Cerebral infarction
  • It has been reliably suggested that Creatine kinase is a reliable biochemical marker of myositis in Dermatomyositis, Serum muscle enzymes, especially the transaminases, creatine kinase (CK), and aldolase, are usually elevated; the 'most sensitive and useful' is CK.
  • Periodic enzyme determinations are helpful in monitoring treatment.
  • Elevated levels decrease with effective therapy.
DIAGNOSIS:
  • Muscle enzyme levels are often abnormal during the course of dermatomyositis, except in patients with amyopathic dermatomyositis (ADM). 
  • The most sensitive/specific enzyme abnormality is elevated creatine kinase (CK), but aldolase studies and other tests (eg, for aspartate aminotransferase [AST] or lactic dehydrogenase [LDH]) may also yield abnormal results.
  • First-line therapy is to recognize that the patient is photosensitive and to prescribe sun avoidance and sun protection measures, including broad-spectrum sunscreens and photoprotective clothing.
  • Hydroxychloroquine and chloroquine have been beneficial .however roughly 25-30% of patients with dermatomyositis who are treated with hydroxychloroquine develop a drug eruption, and patients should be counseled regarding this potential side effect.
  • Methotrexate is often considered first-line systemic therapy if antimalarial fail or are contraindicated.
Exam Question
  • Groton's sign is seen in Dermatomyositis
  • Heliotrope rash is seen in Dermatomyositis
  • Gottrens papules, Helitrope rash & Mechanics hand is seen in Dermatomyositis
  • Perifascicular atropy of muscle fibres is seen in Dermatomyositis
  • A 40 year old woman presented with a 8 month history of erythema and swelling of the periorbital region & papules & plaques on the dorsolateral aspect of forearms & knuckles with ragged cuticles. There was no muscle weakness is diagnosed to have dermatomyositis


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